Media 11 error

Vista x64 medai player 11. This error comes up on some music files not all.

"you media player usage rights have become corrupted or are no longer valid. this might happen if you have replaced hardware componenets in your computer"

NO hardware has been replaced or altered.

Are these files that you ripped from CD, or are they DRM protected files that were downloaded?

It's not my computer, but from looking at them i would guess either ripped or downloaded.