Lost audio on all .avi files

Recently I have lost all audio on my .avi files that I have brought from my digital camera. All past and present files are being affected. I know it's not my camera because I tried uploading the files to a macbook and the audio was still there. I do have all the audio for my OS and applications, and itunes. I feel like i've tried everything. I've opened garage band to see if that would fix it. I repaired permissions in the disk utility. I downloaded real player to see if they would work in there. I uploaded them into imovie and saved them as another type of file to see if that would work, but nothing. When I upload the movies to my blog the audio isn't there, but 2 weeks ago when I uploaded a different movie on, the audio was there.
Any help would be appreciated. I know the audio is there somewhere because I uploaded a .avi file back on to my camera and the audio is there.

Have you tried opening your videos in VLC or MPlayer? The camera may be encoding them with an audio stream that is unreadable by QuickTime/iMovie/RealPlayer.

Give VLC player a try, it should play any video format

Another vote for VLC - totally awesome, never had a problem with it.