If you encountered this error, then
your FairUse4WM is not compatible with IBX verison 11.0.6000.6324. Your IBX version is basically like a template to how the keys to play your audio/video files are created.

You may try to roll back your Windows Media Player to a previous version.

You may also try a virtual machine (either VMWare or Microsoft Virtual PC). Just install Windows XP (assuming you have your Windows XP install/upgrade disc) on it and run the beta version of WMP 11 if your purchase requires it.

And NEVER UPGRADE your WMP. If your DRM-licensed media files require an upgrade to WMP 11 use WMP 11 beta 2 or WMP11 beta 3!

Windows Vista users please read the following forum thread: Help to remove DRM on Windows Vista.