Is there any way you can see the converted files on a PC? I ask because I transcoded a bunch of QT files to AVI and on my mac they played back choppy and had no sound, but when I played them back on my bro's PC, they worked fine. They obviously took a hit in IQ, but it wasn't so bad, and they played smoothly with good sound.
In my experience though, I've never really found a good way of making HD AVI files on my mac, so perhaps someone else can tell us why?