I know for a fact that converting to WebM with MVC and uploading to YouTube works because I've done it. Did you try WebM?
I put something from Imovie into it and I didn't work.
Same with QTP (Quick Time Player)
Here is my Output: mpeg -i /Users/silentnight/Like a G6 .iMovieProject -f webm -vcodec libvpx_vp8 -acodec libvorbis -ab 160000 -sameq /Users/silentnight/Like a G6 .webm
FFmpeg version UNKNOWN, Copyright (c) 2000-2010 the FFmpeg developers
built on May 23 2010 09:25:30 with gcc 4.2.1 (Apple Inc. build 5646) (dot 1)
configuration: --prefix=/Users/cworth/OtherApps/ffmpeg/ffmpeg/../local/x86_64 --enable-static --enable-shared --enable-gpl --enable-version3 --enable-libmp3lame --enable-pthreads --enable-libvorbis --enable-libx264 --enable-libxvid --enable-libfaad --enable-libspeex --enable-libopencore_amrwb --enable-libopencore_amrnb --enable-libvpx-vp8 --enable-memalign-hack --disable-debug --disable-stripping --arch=x86_64
libavutil 50.15. 2 / 50.15. 2
libavcodec 52.68. 0 / 52.68. 0
libavformat 52.62. 0 / 52.62. 0
libavdevice 52. 2. 0 / 52. 2. 0
libavfilter 1.20. 0 / 1.20. 0
libswscale 0.10. 0 / 0.10. 0
/Users/silentnight/Like a G6 .iMovieProject: Operation not permitted