The artifacts are back, with a vengeance

[Mr. Johnson]

Right, for those of you that still remember, I had problems with my ATI card quite a while ago, and everything I did somehow resulted in artifacts.
After much shipping back and forth, I came to the conclusion that my Nvidia mobo was breaking my ATI cards. It was a pretty unsatisfactory outcoming, but at least it gave me a solution to my problem, which was to buy an Nvidia card.
Problem solved, or so I thought.
Since a while now, these artifacts are popping back up, at first I thought it was random, but it seems to have a preference for source games and for some odd reason it did it every single time that I played Indiana Jones and the fate of Atlantis. Now that was odd (it is played in a window, if that helps).
At first I thought it was simply overheating, due to the weather and this house's inability to cool down enough, but seeing as how he did it before it could well be due to a broken motherboard.
Now, I still have guarantee on the thing, so I could have them change it, but that means I'll be without a pc for a few weeks, so could it simply be due to the heat and if not, is there anything else I should check out before I rush into this?

Cheers guys.

[Grimmie]

http://www.memtest.org/

/standard hardware forum reply

[Dr. kitteny berk]

Also scan for artifacts in ATItool (yes, it works on nvidia cards)