I'm using the current SVN version of mlt, mlt++ and kdenlive on Ubuntu Feisty, built using the following procedure:

cd mlt
./configure --prefix=/usr --enable-gpl --enable-shared --enable-theora --enable-vorbis --enable-libogg --enable-pp --enable-shared-pp --enable-motion-est --avformat-swscale && make && echo OK
sudo make install && echo OK

cd ../mlt++/
./configure --prefix=/usr && make && echo OK
sudo make install && echo OK

cd ../kdenlive/
sh bootstrap && ./configure --prefix=/usr --enable-debug=full && unsermake && echo OK
sudo unsermake install && echo OK

KDEnlive overall works fine (regarding basic functions like importing clips, placing on the timeline, adding transitions, saving the project, loading the project, exporting to XviD), but it crashes every time I try to save layout and upon exit (probably due to saving options).

Here's the full backtrace from crash when saving layout:

Using host libthread_db library "/lib/tls/i686/cmov/libthread_db.so.1".
[Thread debugging using libthread_db enabled]
[New Thread -1208870448 (LWP 6515)]
[New Thread -1221743728 (LWP 6519)]
[New Thread -1230136432 (LWP 6518)]
[KCrash handler]
#6  0x4572408c in internalLatin1ToUnicode (
    str=0x1770 
, len=0xbf865d34, 
    maxlen=4294967295) at tools/qstring.cpp:1189
#7  0x45724137 in QString::fromLatin1 (
    chars=0x1770 
, len=-1)
    at tools/qstring.cpp:5933
#8  0x46532347 in KDockManager::writeConfig (this=0x82ded48, c=0x826b160, 
    group=@0xbf86607c)
    at /build/buildd/kdelibs-3.5.6/./kdecore/kconfigbase.h:1002
#9  0x46532481 in KDockMainWindow::writeDockConfig (this=0x82da1a8, 
    c=0x826b160, group=@0xbf8660b4)
    at /build/buildd/kdelibs-3.5.6/./kdeui/kdockwidget.cpp:170
#10 0x0811abf2 in Gui::KdenliveApp::saveLayout1 (this=0x82da1a8)
    at /home/opt/soft/Graphics/KDEnlive/SVN/build/2007-06-09/kdenlive/kdenlive/kdenlive.cpp:3796
#11 0x081d6938 in Gui::KdenliveApp::qt_invoke (this=0x82da1a8, _id=161, 
    _o=0xbf86628c) at ./kdenlive/kdenlive.moc.cpp:721
#12 0x45408e4b in QObject::activate_signal (this=0x8339ba8, clist=0x8339db0, 
    o=0xbf86628c) at kernel/qobject.cpp:2356
#13 0x454098f0 in QObject::activate_signal (this=0x8339ba8, signal=2)
    at kernel/qobject.cpp:2325
#14 0x4643c4c9 in KAction::activated (this=0x8339ba8) at ./kaction.moc:176
#15 0x46474cc2 in KAction::slotActivated (this=0x8339ba8)
    at /build/buildd/kdelibs-3.5.6/./kdeui/kaction.cpp:1102
#16 0x4654206d in KAction::slotPopupActivated (this=0x8339ba8)
    at /build/buildd/kdelibs-3.5.6/./kdeui/kaction.cpp:1137
#17 0x46542331 in KAction::qt_invoke (this=0x8339ba8, _id=16, _o=0xbf8663c8)
    at ./kaction.moc:219
#18 0x45408e4b in QObject::activate_signal (this=0x8356328, clist=0x8355e20, 
    o=0xbf8663c8) at kernel/qobject.cpp:2356
#19 0x457950a0 in QSignal::signal (this=0x8356328, t0=@0x8356350)
    at .moc/debug-shared-mt/moc_qsignal.cpp:100
#20 0x45428dde in QSignal::activate (this=0x8356328) at kernel/qsignal.cpp:212
#21 0x4552f4db in QPopupMenu::mouseReleaseEvent (this=0x83a0320, e=0xbf866910)
    at widgets/qpopupmenu.cpp:1697
#22 0x4644334e in KPopupMenu::mouseReleaseEvent (this=0x83a0320, e=0xbf866910)
    at /build/buildd/kdelibs-3.5.6/./kdeui/kpopupmenu.cpp:508
#23 0x4543fc1d in QWidget::event (this=0x83a0320, e=0xbf866910)
    at kernel/qwidget.cpp:4702
#24 0x453a0020 in QApplication::internalNotify (this=0xbf866f2c, 
    receiver=0x83a0320, e=0xbf866910) at kernel/qapplication.cpp:2635
#25 0x453a21de in QApplication::notify (this=0xbf866f2c, receiver=0x83a0320, 
    e=0xbf866910) at kernel/qapplication.cpp:2421
#26 0x46252e82 in KApplication::notify (this=0xbf866f2c, receiver=0x83a0320, 
    event=0xbf866910)
    at /build/buildd/kdelibs-3.5.6/./kdecore/kapplication.cpp:550
#27 0x4533281d in QApplication::sendSpontaneousEvent (receiver=0x83a0320, 
    event=0xbf866910) at kernel/qapplication.h:523
#28 0x4533115f in QETWidget::translateMouseEvent (this=0x83a0320, 
    event=0xbf866d68) at kernel/qapplication_x11.cpp:4245
#29 0x4532f56c in QApplication::x11ProcessEvent (this=0xbf866f2c, 
    event=0xbf866d68) at kernel/qapplication_x11.cpp:3480
#30 0x45346740 in QEventLoop::processEvents (this=0x8268bb0, flags=4)
    at kernel/qeventloop_x11.cpp:192
#31 0x453ba6f6 in QEventLoop::enterLoop (this=0x8268bb0)
    at kernel/qeventloop.cpp:198
#32 0x453ba506 in QEventLoop::exec (this=0x8268bb0)
    at kernel/qeventloop.cpp:145
#33 0x453a1bc9 in QApplication::exec (this=0xbf866f2c)
    at kernel/qapplication.cpp:2758
#34 0x08183e6e in main (argc=136455852, argv=0xbf8670a4)
    at /home/opt/soft/Graphics/KDEnlive/SVN/build/2007-06-09/kdenlive/kdenlive/main.cpp:107

And here's backtrace from crash on exiting KDEnlive:

Using host libthread_db library "/lib/tls/i686/cmov/libthread_db.so.1".
[Thread debugging using libthread_db enabled]
[New Thread -1208579632 (LWP 7085)]
[New Thread -1229845616 (LWP 7116)]
[New Thread -1221452912 (LWP 7115)]
[KCrash handler]
#6  0x4572408c in internalLatin1ToUnicode (
    str=0x1777 
, len=0xbfbab384, 
    maxlen=4294967295) at tools/qstring.cpp:1189
#7  0x45724137 in QString::fromLatin1 (
    chars=0x1777 
, len=-1)
    at tools/qstring.cpp:5933
#8  0x46532347 in KDockManager::writeConfig (this=0x82ded18, c=0x826b198, 
    group=@0xbfbab6cc)
    at /build/buildd/kdelibs-3.5.6/./kdecore/kconfigbase.h:1002
#9  0x46532481 in KDockMainWindow::writeDockConfig (this=0x82da180, 
    c=0x826b198, group=@0xbfbab720)
    at /build/buildd/kdelibs-3.5.6/./kdeui/kdockwidget.cpp:170
#10 0x08128eb5 in Gui::KdenliveApp::saveOptions (this=0x82da180)
    at /home/opt/soft/Graphics/KDEnlive/SVN/build/2007-06-09/kdenlive/kdenlive/kdenlive.cpp:1946
#11 0x0812911e in Gui::KdenliveApp::queryClose (this=0x82da180)
    at /home/opt/soft/Graphics/KDEnlive/SVN/build/2007-06-09/kdenlive/kdenlive/kdenlive.cpp:2024
#12 0x46528b67 in KMainWindow::closeEvent (this=0x82da180, e=0xbfbabb28)
    at /build/buildd/kdelibs-3.5.6/./kdeui/kmainwindow.cpp:640
#13 0x4544007b in QWidget::event (this=0x82da180, e=0xbfbabb28)
    at kernel/qwidget.cpp:4818
#14 0x45516166 in QMainWindow::event (this=0x82da180, e=0xbfbabb28)
    at widgets/qmainwindow.cpp:1687
#15 0x453a0020 in QApplication::internalNotify (this=0xbfbac05c, 
    receiver=0x82da180, e=0xbfbabb28) at kernel/qapplication.cpp:2635
#16 0x453a29ea in QApplication::notify (this=0xbfbac05c, receiver=0x82da180, 
    e=0xbfbabb28) at kernel/qapplication.cpp:2523
#17 0x46252e82 in KApplication::notify (this=0xbfbac05c, receiver=0x82da180, 
    event=0xbfbabb28)
    at /build/buildd/kdelibs-3.5.6/./kdecore/kapplication.cpp:550
#18 0x453327a9 in QApplication::sendEvent (receiver=0x82da180, 
    event=0xbfbabb28) at ../include/qapplication.h:520
#19 0x45442b11 in QWidget::close (this=0x82da180, alsoDelete=false)
    at kernel/qwidget.cpp:4288
#20 0x4531edf2 in QETWidget::translateCloseEvent (this=0x82da180)
    at kernel/qapplication_x11.cpp:5925
#21 0x453248b3 in QApplication::x11ClientMessage (this=0xbfbac05c, 
    w=0x82da180, event=0xbfbabe98, passive_only=false)
    at kernel/qapplication_x11.cpp:3152
#22 0x4532fe96 in QApplication::x11ProcessEvent (this=0xbfbac05c, 
    event=0xbfbabe98) at kernel/qapplication_x11.cpp:3643
#23 0x45346740 in QEventLoop::processEvents (this=0x8268be8, flags=4)
    at kernel/qeventloop_x11.cpp:192
#24 0x453ba6f6 in QEventLoop::enterLoop (this=0x8268be8)
    at kernel/qeventloop.cpp:198
#25 0x453ba506 in QEventLoop::exec (this=0x8268be8)
    at kernel/qeventloop.cpp:145
#26 0x453a1bc9 in QApplication::exec (this=0xbfbac05c)
    at kernel/qapplication.cpp:2758
#27 0x08183e6e in main (argc=136455852, argv=0xbfbac1d4)
    at /home/opt/soft/Graphics/KDEnlive/SVN/build/2007-06-09/kdenlive/kdenlive/main.cpp:107

It seems that the crashes are related to charset translations, so here are my locale settings just in case:

$ locale
LANG=en_US.UTF-8
LANGUAGE=en_US.UTF-8
LC_CTYPE=pl_PL.UTF-8
LC_NUMERIC=pl_PL.UTF-8
LC_TIME=pl_PL.UTF-8
LC_COLLATE=pl_PL.UTF-8
LC_MONETARY=pl_PL.UTF-8
LC_MESSAGES=pl_PL.UTF-8
LC_PAPER=pl_PL.UTF-8
LC_NAME=pl_PL.UTF-8
LC_ADDRESS=pl_PL.UTF-8
LC_TELEPHONE=pl_PL.UTF-8
LC_MEASUREMENT=pl_PL.UTF-8
LC_IDENTIFICATION="en_US.UTF-8"
LC_ALL=

BTW, here are backtraces from all threads made using gdb.

Backtrace from simply exiting KDEnlive:

kdenlive: Mlt inited
[New Thread -1215947888 (LWP 31886)]
[New Thread -1224340592 (LWP 31887)]
[Thread -1215947888 (LWP 31886) exited]
[Thread -1224340592 (LWP 31887) exited]
[New Thread -1224340592 (LWP 31888)]
[New Thread -1215947888 (LWP 31889)]

Program received signal SIGSEGV, Segmentation fault.
[Switching to Thread -1209058864 (LWP 31883)]
0x4572408c in internalLatin1ToUnicode (str=0x176f 
, len=0xbfca8804, maxlen=4294967295) at tools/qstring.cpp:1189
1189    tools/qstring.cpp: No such file or directory.
        in tools/qstring.cpp
(gdb) thread apply all bt

Thread 5 (Thread -1215947888 (LWP 31889)):
#0  0xffffe410 in __kernel_vsyscall ()
#1  0x45bc45c6 in pthread_cond_wait@@GLIBC_2.3.2 () from /lib/tls/i686/cmov/libpthread.so.0
#2  0xb7aad3a6 in consumer_thread (arg=0x8532aa0) at consumer_sdl_preview.c:381
#3  0x45bc031b in start_thread () from /lib/tls/i686/cmov/libpthread.so.0
#4  0x45b1857e in clone () from /lib/tls/i686/cmov/libc.so.6

Thread 4 (Thread -1224340592 (LWP 31888)):
#0  0xffffe410 in __kernel_vsyscall ()
#1  0x45bc484c in pthread_cond_timedwait@@GLIBC_2.3.2 () from /lib/tls/i686/cmov/libpthread.so.0
#2  0xb7f657e9 in mlt_consumer_get_frame (this=0x8523b28) at mlt_consumer.c:298
#3  0xb7f659ad in mlt_consumer_rt_frame (this=0x8523b28) at mlt_consumer.c:792
#4  0xb7aad85d in consumer_thread (arg=0x8523b28) at consumer_sdl_still.c:560
#5  0x45bc031b in start_thread () from /lib/tls/i686/cmov/libpthread.so.0
#6  0x45b1857e in clone () from /lib/tls/i686/cmov/libc.so.6

Thread 1 (Thread -1209058864 (LWP 31883)):
#0  0x4572408c in internalLatin1ToUnicode (str=0x176f 
, len=0xbfca8804, maxlen=4294967295) at tools/qstring.cpp:1189
#1  0x45724137 in QString::fromLatin1 (chars=0x176f 
, len=-1) at tools/qstring.cpp:5933
#2  0x46532347 in KDockManager::writeConfig (this=0x82d4b80, c=0x826d8a0, group=@0xbfca8b4c) at /build/buildd/kdelibs-3.5.6/./kdecore/kconfigbase.h:1002
#3  0x46532481 in KDockMainWindow::writeDockConfig (this=0x827b620, c=0x826d8a0, group=@0xbfca8ba0) at /build/buildd/kdelibs-3.5.6/./kdeui/kdockwidget.cpp:170
#4  0x081291b5 in Gui::KdenliveApp::saveOptions (this=0x827b620) at /home/opt/soft/Graphics/KDEnlive/SVN/build/2007-06-10.2/kdenlive/kdenlive/kdenlive.cpp:1946
#5  0x0812941e in Gui::KdenliveApp::queryClose (this=0x827b620) at /home/opt/soft/Graphics/KDEnlive/SVN/build/2007-06-10.2/kdenlive/kdenlive/kdenlive.cpp:2024
#6  0x46528b67 in KMainWindow::closeEvent (this=0x827b620, e=0xbfca8fa8) at /build/buildd/kdelibs-3.5.6/./kdeui/kmainwindow.cpp:640
#7  0x4544007b in QWidget::event (this=0x827b620, e=0xbfca8fa8) at kernel/qwidget.cpp:4818
#8  0x45516166 in QMainWindow::event (this=0x827b620, e=0xbfca8fa8) at widgets/qmainwindow.cpp:1687
#9  0x453a0020 in QApplication::internalNotify (this=0xbfca94dc, receiver=0x827b620, e=0xbfca8fa8) at kernel/qapplication.cpp:2635
#10 0x453a29ea in QApplication::notify (this=0xbfca94dc, receiver=0x827b620, e=0xbfca8fa8) at kernel/qapplication.cpp:2523
#11 0x46252e82 in KApplication::notify (this=0xbfca94dc, receiver=0x827b620, event=0xbfca8fa8) at /build/buildd/kdelibs-3.5.6/./kdecore/kapplication.cpp:550
#12 0x453327a9 in QApplication::sendEvent (receiver=0x827b620, event=0xbfca8fa8) at ../include/qapplication.h:520
#13 0x45442b11 in QWidget::close (this=0x827b620, alsoDelete=false) at kernel/qwidget.cpp:4288
#14 0x4531edf2 in QETWidget::translateCloseEvent (this=0x827b620) at kernel/qapplication_x11.cpp:5925
#15 0x453248b3 in QApplication::x11ClientMessage (this=0xbfca94dc, w=0x827b620, event=0xbfca9318, passive_only=false) at kernel/qapplication_x11.cpp:3152
#16 0x4532fe96 in QApplication::x11ProcessEvent (this=0xbfca94dc, event=0xbfca9318) at kernel/qapplication_x11.cpp:3643
#17 0x45346740 in QEventLoop::processEvents (this=0x826ca38, flags=4) at kernel/qeventloop_x11.cpp:192
#18 0x453ba6f6 in QEventLoop::enterLoop (this=0x826ca38) at kernel/qeventloop.cpp:198
#19 0x453ba506 in QEventLoop::exec (this=0x826ca38) at kernel/qeventloop.cpp:145
#20 0x453a1bc9 in QApplication::exec (this=0xbfca94dc) at kernel/qapplication.cpp:2758
#21 0x0818416e in main (argc=136472940, argv=0xbfca9654) at /home/opt/soft/Graphics/KDEnlive/SVN/build/2007-06-10.2/kdenlive/kdenlive/main.cpp:107
(gdb) 

Backtrace from saving layout 1:

kdenlive: Mlt inited
[New Thread -1215960176 (LWP 31973)]
[New Thread -1224352880 (LWP 31974)]
[Thread -1215960176 (LWP 31973) exited]
[Thread -1224352880 (LWP 31974) exited]
[New Thread -1224352880 (LWP 31975)]
[New Thread -1215960176 (LWP 31976)]

Program received signal SIGSEGV, Segmentation fault.
[Switching to Thread -1209071152 (LWP 31950)]
0x4572408c in internalLatin1ToUnicode (str=0x1777 
, len=0xbfcc9304, maxlen=4294967295) at tools/qstring.cpp:1189
1189    tools/qstring.cpp: No such file or directory.
        in tools/qstring.cpp
(gdb) thread apply all bt

Thread 5 (Thread -1215960176 (LWP 31976)):
#0  0xffffe410 in __kernel_vsyscall ()
#1  0x45bc45c6 in pthread_cond_wait@@GLIBC_2.3.2 () from /lib/tls/i686/cmov/libpthread.so.0
#2  0xb7aaa3a6 in consumer_thread (arg=0x8531358) at consumer_sdl_preview.c:381
#3  0x45bc031b in start_thread () from /lib/tls/i686/cmov/libpthread.so.0
#4  0x45b1857e in clone () from /lib/tls/i686/cmov/libc.so.6

Thread 4 (Thread -1224352880 (LWP 31975)):
#0  0xffffe410 in __kernel_vsyscall ()
#1  0x45bc484c in pthread_cond_timedwait@@GLIBC_2.3.2 () from /lib/tls/i686/cmov/libpthread.so.0
#2  0xb7f627e9 in mlt_consumer_get_frame (this=0x85221e8) at mlt_consumer.c:298
#3  0xb7f629ad in mlt_consumer_rt_frame (this=0x85221e8) at mlt_consumer.c:792
#4  0xb7aaa85d in consumer_thread (arg=0x85221e8) at consumer_sdl_still.c:560
#5  0x45bc031b in start_thread () from /lib/tls/i686/cmov/libpthread.so.0
#6  0x45b1857e in clone () from /lib/tls/i686/cmov/libc.so.6

Thread 1 (Thread -1209071152 (LWP 31950)):
#0  0x4572408c in internalLatin1ToUnicode (str=0x1777 
, len=0xbfcc9304, maxlen=4294967295) at tools/qstring.cpp:1189
#1  0x45724137 in QString::fromLatin1 (chars=0x1777 
, len=-1) at tools/qstring.cpp:5933
#2  0x46532347 in KDockManager::writeConfig (this=0x82d4b80, c=0x826d8a0, group=@0xbfcc964c) at /build/buildd/kdelibs-3.5.6/./kdecore/kconfigbase.h:1002
#3  0x46532481 in KDockMainWindow::writeDockConfig (this=0x827b620, c=0x826d8a0, group=@0xbfcc9684) at /build/buildd/kdelibs-3.5.6/./kdeui/kdockwidget.cpp:170
#4  0x0811aef2 in Gui::KdenliveApp::saveLayout1 (this=0x827b620) at /home/opt/soft/Graphics/KDEnlive/SVN/build/2007-06-10.2/kdenlive/kdenlive/kdenlive.cpp:3796
#5  0x081da794 in Gui::KdenliveApp::qt_invoke (this=0x827b620, _id=161, _o=0xbfcc985c) at ./kdenlive/kdenlive.moc.cpp:721
#6  0x45408e4b in QObject::activate_signal (this=0x833d750, clist=0x833d958, o=0xbfcc985c) at kernel/qobject.cpp:2356
#7  0x454098f0 in QObject::activate_signal (this=0x833d750, signal=2) at kernel/qobject.cpp:2325
#8  0x4643c4c9 in KAction::activated (this=0x833d750) at ./kaction.moc:176
#9  0x46474cc2 in KAction::slotActivated (this=0x833d750) at /build/buildd/kdelibs-3.5.6/./kdeui/kaction.cpp:1102
#10 0x4654206d in KAction::slotPopupActivated (this=0x833d750) at /build/buildd/kdelibs-3.5.6/./kdeui/kaction.cpp:1137
#11 0x46542331 in KAction::qt_invoke (this=0x833d750, _id=16, _o=0xbfcc9998) at ./kaction.moc:219
#12 0x45408e4b in QObject::activate_signal (this=0x835ec38, clist=0x835ee58, o=0xbfcc9998) at kernel/qobject.cpp:2356
#13 0x457950a0 in QSignal::signal (this=0x835ec38, t0=@0x835ec60) at .moc/debug-shared-mt/moc_qsignal.cpp:100
#14 0x45428dde in QSignal::activate (this=0x835ec38) at kernel/qsignal.cpp:212
#15 0x4552f4db in QPopupMenu::mouseReleaseEvent (this=0x83a50c8, e=0xbfcc9ee0) at widgets/qpopupmenu.cpp:1697
#16 0x4644334e in KPopupMenu::mouseReleaseEvent (this=0x83a50c8, e=0xbfcc9ee0) at /build/buildd/kdelibs-3.5.6/./kdeui/kpopupmenu.cpp:508
#17 0x4543fc1d in QWidget::event (this=0x83a50c8, e=0xbfcc9ee0) at kernel/qwidget.cpp:4702
#18 0x453a0020 in QApplication::internalNotify (this=0xbfcca4fc, receiver=0x83a50c8, e=0xbfcc9ee0) at kernel/qapplication.cpp:2635
#19 0x453a21de in QApplication::notify (this=0xbfcca4fc, receiver=0x83a50c8, e=0xbfcc9ee0) at kernel/qapplication.cpp:2421
#20 0x46252e82 in KApplication::notify (this=0xbfcca4fc, receiver=0x83a50c8, event=0xbfcc9ee0) at /build/buildd/kdelibs-3.5.6/./kdecore/kapplication.cpp:550
#21 0x4533281d in QApplication::sendSpontaneousEvent (receiver=0x83a50c8, event=0xbfcc9ee0) at kernel/qapplication.h:523
#22 0x4533115f in QETWidget::translateMouseEvent (this=0x83a50c8, event=0xbfcca338) at kernel/qapplication_x11.cpp:4245
#23 0x4532f56c in QApplication::x11ProcessEvent (this=0xbfcca4fc, event=0xbfcca338) at kernel/qapplication_x11.cpp:3480
#24 0x45346740 in QEventLoop::processEvents (this=0x826ca38, flags=4) at kernel/qeventloop_x11.cpp:192
#25 0x453ba6f6 in QEventLoop::enterLoop (this=0x826ca38) at kernel/qeventloop.cpp:198
#26 0x453ba506 in QEventLoop::exec (this=0x826ca38) at kernel/qeventloop.cpp:145
#27 0x453a1bc9 in QApplication::exec (this=0xbfcca4fc) at kernel/qapplication.cpp:2758
#28 0x0818416e in main (argc=136472940, argv=0xbfcca674) at /home/opt/soft/Graphics/KDEnlive/SVN/build/2007-06-10.2/kdenlive/kdenlive/main.cpp:107

The crashes are caused by some old stuff from KDEnlive 0.4 - when I've deleted ~/.kde/share/apps/kdenlive/ and

~/.kde/share/config/kdenliverc, they'he stopped occuring.