Sounds more like a problem with QT. Have you played the file in any other media players - MPEG Streamclip, VLC, Flip player, Cineplay (an iOS media player), etc.
I don't trust QT7 for too many things. It has quite a few bugs and sometimes displays the beginnings of my videos incorrectly too. Confirm other media players produce the same result before blaming AME.
Ryan Holmes
http://www.ryanholmes.me
@CutColorPost