I installed the precompiled ubuntu packages per you site. When I try to render to web (youtube) all listed items are displayed in red with a circled X.

i am using 10.04 and kdenlive .8 as well. are you using the medibuntu lucid repository for the FFMPEG software libs that have aac encoding enabled? I actually just ran into an issue when I tried to render to x264 profile which has aac audio. it worked on 9/14/2011 and now for some reason it stopped working. it renders but there is no audio at all. when I use mediainfo on the resulting .mp4 file, there's no audio codec listed. then when i issue ffmpeg -formats | grep aac it only shows a "D" for aac which means FFMPEG only has decoding enabled and not ENCODING. I didn't change anything either, at least not on purpose. LOL

So, i am currently trying to figure out whats going on as well. It successfully rendered to .mp4 (x264/aac) on Sept 14 and now it doesn't. Here's what it says when I issue ffmpeg -formats | grep aac

FFmpeg version SVN-r0.5.1-4:0.5.1-1ubuntu1.2, Copyright (c) 2000-2009 Fabrice Bellard, et al.
configuration: --extra-version=4:0.5.1-1ubuntu1.2 --prefix=/usr --enable-avfilter --enable-avfilter-lavf --enable-vdpau --enable-bzlib --enable-libgsm --enable-libschroedinger --enable-libspeex --enable-libtheora --enable-libvorbis --enable-pthreads --enable-zlib --disable-stripping --disable-vhook --enable-runtime-cpudetect --enable-gpl --enable-postproc --enable-swscale --enable-x11grab --enable-libdc1394 --enable-shared --disable-static
libavutil 49.15. 0 / 49.15. 0
libavcodec 52.20. 1 / 52.20. 1
libavformat 52.31. 0 / 52.31. 0
libavdevice 52. 1. 0 / 52. 1. 0
libavfilter 0. 4. 0 / 0. 4. 0
libswscale 0. 7. 1 / 0. 7. 1
libpostproc 51. 2. 0 / 51. 2. 0
built on Sep 16 2011 17:04:18, gcc: 4.4.3
D aac raw ADTS AAC
D A aac Advanced Audio Coding

I am using sunab ppa = http://ppa.launchpad.net/sunab/kdenlive-release/ubuntu
the medibuntu repo = http://packages.medibuntu.org/ free non-free

Any help would be appreciated!

well, i don't know what the heck is going on. using synaptic I hit check all upgrades/updates and it found nothing. BUT when i open the update manager, click check, it finds all the lib*******-extra-52 etc etc libraries and now my ffmpeg is back to being able to ENCODE aac audio. Issuing
ffmpeg -formats | grep aac

FFmpeg version SVN-r0.5.1-4:0.5.1-1ubuntu1.2, Copyright (c) 2000-2009 Fabrice Bellard, et al.
configuration: --extra-version=4:0.5.1-1ubuntu1.2 --prefix=/usr --enable-avfilter --enable-avfilter-lavf --enable-vdpau --enable-bzlib --enable-libgsm --enable-libschroedinger --enable-libspeex --enable-libtheora --enable-libvorbis --enable-pthreads --enable-zlib --disable-stripping --disable-vhook --enable-runtime-cpudetect --enable-gpl --enable-postproc --enable-swscale --enable-x11grab --enable-libdc1394 --enable-shared --disable-static
libavutil 49.15. 0 / 49.15. 0
libavcodec 52.20. 1 / 52.20. 1
libavformat 52.31. 0 / 52.31. 0
libavdevice 52. 1. 0 / 52. 1. 0
libavfilter 0. 4. 0 / 0. 4. 0
libswscale 0. 7. 1 / 0. 7. 1
libpostproc 51. 2. 0 / 51. 2. 0
built on Sep 16 2011 17:04:18, gcc: 4.4.3
D aac raw ADTS AAC
D A aac Advanced Audio Coding
EA libfaac libfaac AAC (Advanced Audio Codec)

all is ok again.