guys, help me figure this thing out

[Caged Anger]

This is happening more and more frequently. I go to play quake or play Unreal and I get an error box, the mouse won't move and I have to alt F4 and restart. When it comes back online, the screen has been reset to 800 X 600. What could be causing this? it's never happened like this before :hmmm:

[SALvation]

What's the error say?

[Caged Anger]

says an unknown error has occured but the file it occurs in keeps changing