Pity you're not still around but if you do see this & still need to know, go to QT's preferences & check Update tab & tick find & install new 3rd party software. That's not the only 3rd party plugs you should get though.

Have you tried viewing it with another player? eg: VLC (has built in codecs, & choose nearest mirror site) or MPlayer And also ensure you have the latest 3rd party codecs for QT such as 1. DivX, 2. XviD, 3. 3ivx , etc.

If possible also get MPeg2 playback codec. If you have Final Cut Pro or DVD Studio Pro then this will come with them plus the ability to encode to MPeg 2.

Personally I have set QT as default to play MPEG files & VLC as default to play AVI & wmv files, etc.