Problem with shuting down my computer

Hello,

I do like CrossFire and I don't want to stop playing it. But I noticed a problem which is quite strange.
First off, I'm on Windows Vista (Service Pack 2, if this information is needed). Everything works fine with the Game itself, but every time I quit the game after playinf for a while, I cn't shut down my computer anymore. This happens only after playing CF. I need to remove the computer from the socket to get it off.
When I try to start up my computer again, everything works well, but sometimes my desktop appears without anything on it, so I have to restart my computer in save mode.

I really don't want to stop playing CF, but this error is quite problematic.

Thanks in advance.

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