WMP9 unknown error

I have an mpg file that when I try to play gives Windows Media Player 9 an “unknown error”. I have tried FourCC changer and nothing happens. I have tried to convert it to other formats, but it still doesn’t play, so I think it is a codec problem. I would appreciate any help on this. Thanks.

Are you sure that WMP is up to date ? I’ve had a series of similar problems, and usually get a message that my DRM (Digital Rights Management) isn’t up to date, and that I need to update the player (not the codec). As I have no intention of letting M$ put DRM on my computer, I find different files to play