Hey LMACINNIS,
Have you tried installing perian - it has loads of codecs for playing movies (I'm thinking it might be codec related and nothing to do with your USB device.)
I personally use Quicktime and VLC to play back my movies as sometimes one will work better than the other - depending on how the movie was encoded. (I also have perian installed)
here is a -
link - to perian, it's free to download and use.