No audio but good video when playing back RTVB files

Hi guys,
I think I may have a codec issue with my 10GB or RMVB files I want to playback using the ATV files. THe video plays back fine but there is no audio. The files playback perfectly on my other laptops. What’s the best way to isolate the problem and find out how the audio stream is encoded to look into why the audio is not being played on the ATV?

If this is a version thing - do you know ofany tools that can be used to update the disfunctional audio stream to one that will work on this machine? It was afterall one of the main reasons I went out and purchased/instsalled the AppleTV and ATVFlash stuff.

Has anyone experienced this before and can make a suggestion on how to either fix or workaround it?