video card problems i think?

Hello,
I have an x800 xt platinum msi card. I now have a new problem and im not sure what is causing it. It usually happens when i load up my unreal tournament game. the screen goes crazy and all i can see is little squares sometimes it looks like stitches but everything turns rainbow colored and i cant read anything. I can still faintly make out the desktop. I can reboot it and most of the time its fine again till i try and reload game, other times it runs perfectly fine for a while then bam problems back. the game runs fine and isnt the problem btw.

I dl'ed ati tool and my normal temp is about 42 for the vid card.I also have a zalman heatsink and fan on the card. I leave my case door off as it lets my machine run cooler . I removed ati drivers updated to new after i cleaned out old drivers updated to sp2 which is one of only a few updates i have done. I havent updated my windows other than my directx and a few important updates. I removed heatsink cleaned and applied new thermal paste fan is workingon heatsink. theres a big 80mm fan next to vid card that helps cool card .

I have no virus that avg could find and i havent added any parts. Im not sure if its video card or software related. please help thank you