Shutting Down

Okay, so I have two computers, one a windows Vista and one a Windows XP, they both have the same odd problem, before, i could easily shut down both computers, but when i put crossfire on either one, i can still shut down either computer, but when i actually run crossfire, both computers act normally expect when i want to shut either off, they freeze up and i have to force shut them down. Is this new/old just me or anyone else?