Thanks for your response, I appreciate it! I will check the cables one more time and if the fans are clear.

Yeah, overheating is definitely possible, but somehow seems unlikely. Whenever the 3D card is running without the fan blowing at higher or the highest speed, there are no problems.

With a cold system, just booted up and the first thing I try do is play a game, it will crash immediately (when the fan starts spinning faster). You'd expect to at least have some time before overheating would cause the system to crash. I'd expect a few ATI related errors or messages as well in that case, but temperatures seem to stay normal.

The computer shows no signs of issues at all as long as I do not play games, no graphics artifacts in Windows or other programs.

I'm probably going to try to get a new power supply, either the same model but something bigger like a 1000W.