Adobe Bridge .MP4 preview just shows green

Many files dowloaded from youtube show green thumbnails and have a green or white noise image when previewed. But when double clicked and played in QT or finder they play fine. 

I've tried:
- clearing the cache
- moving the cache
- moving the file to my main HDD
- enabling / disabling full screen preview
- enabling / disabling software rendering
- setting all mp4 and quicktime extensions to play with QT
- restarting Bridge
- re-installing Bridge

Any suggestions?

Thanks