I tried to change the default tracker by clicking a tracker in the list and clicking the Change Tracker button, and KTorrent crashed.

(no debugging symbols found)
Using host libthread_db library "/lib/tls/i686/cmov/libthread_db.so.1".
[Thread debugging using libthread_db enabled]
[New Thread -1209792832 (LWP 25665)]
[New Thread -1229489232 (LWP 25776)]
[KCrash handler]
#9 0xb7f66a6f in bt::PeerSourceManager::setTracker ()
from /usr/lib/libktorrent.so.0
#10 0xb6ea7894 in kt::TrackerView::btnChange_clicked ()
from /usr/lib/kde3/ktinfowidgetplugin.so
#11 0xb6eb1019 in TrackerViewBase::qt_invoke ()
from /usr/lib/kde3/ktinfowidgetplugin.so
#12 0xb6ea6b50 in kt::TrackerView::qt_invoke ()
from /usr/lib/kde3/ktinfowidgetplugin.so
#13 0x4754a253 in QObject::activate_signal (this=0x865cad8, clist=0x865eae8,
o=0xbfd58d1c) at kernel/qobject.cpp:2356
#14 0x4754ace4 in QObject::activate_signal (this=0x865cad8, signal=4)
at kernel/qobject.cpp:2325
#15 0x478dc2df in QButton::clicked (this=0x865cad8)
at .moc/debug-shared-mt/moc_qbutton.cpp:152
#16 0x475e71ee in QButton::mouseReleaseEvent (this=0x865cad8, e=0xbfd59184)
at widgets/qbutton.cpp:836
#17 0x47580bf4 in QWidget::event (this=0x865cad8, e=0xbfd59184)
at kernel/qwidget.cpp:4702
#18 0x474e2176 in QApplication::internalNotify (this=0xbfd59760,
receiver=0x865cad8, e=0xbfd59184) at kernel/qapplication.cpp:2635
#19 0x474e4319 in QApplication::notify (this=0xbfd59760, receiver=0x865cad8,
e=0xbfd59184) at kernel/qapplication.cpp:2421
#20 0x47be3fee in KApplication::notify (this=0xbfd59760, receiver=0x865cad8,
event=0xbfd59184)
at /home/sid-user/kdelibs/kdelibs-3.5.5/./kdecore/kapplication.cpp:550
#21 0x474759e5 in QApplication::sendSpontaneousEvent (receiver=0x865cad8,
event=0xbfd59184) at kernel/qapplication.h:523
#22 0x4747467f in QETWidget::translateMouseEvent (this=0x865cad8,
event=0xbfd595b8) at kernel/qapplication_x11.cpp:4301
#23 0x47472c00 in QApplication::x11ProcessEvent (this=0xbfd59760,
event=0xbfd595b8) at kernel/qapplication_x11.cpp:3478
#24 0x47489252 in QEventLoop::processEvents (this=0x80e4b20, flags=4)
at kernel/qeventloop_x11.cpp:192
#25 0x474fc6c9 in QEventLoop::enterLoop (this=0x80e4b20)
at kernel/qeventloop.cpp:198
#26 0x474fc4ea in QEventLoop::exec (this=0x80e4b20)
at kernel/qeventloop.cpp:145
#27 0x474e3d0f in QApplication::exec (this=0xbfd59760)
at kernel/qapplication.cpp:2758
#28 0x08063536 in ?? ()
#29 0x45285ea8 in __libc_start_main () from /lib/tls/i686/cmov/libc.so.6
#30 0x08063091 in ?? ()

I can't reproduce it here, can you send me that torrent ?

I can't reproduce it at the moment either, and I didn't keep track of which torrent it was. Sorry. If it happens again I'll post more info.