Windows Media Player & mp3's

[thegreatsoprendo]

Why is it that WMP plays most mp3's fine, but with a small number it gives an error message saying:

"Windows Media Player cannot play the file. The file is either corrupt or the Player does not support the format you are trying to play."

However, if I open them in RealPlayer, they play without any problems!?

It's WMP v9, btw...