Why do most AVI's and WMV's seem to not work on the PS3?

[Akvod]

wholikeswood said:
Often my AVIs don't show, so I just click Triangle and choose "Display All" or whatever the option is called, and suddenly all the AVIs appear and are playable.

Don't know if that's applicable to your situation, but it's just a common solution.

Now I feel awfully silly.