Every time I try to play a newer game(Skyrim, Saints Row 3) my computer screen goes black after a few minutes. Sometimes it takes 30 minutes and other times it takes 2 minutes. The screen cuts off and the sound continues. After a few seconds the sound cuts out, an alarm sounds, and I have to restart the computer. Everything I have read points to this being a heating issue, but I can't replicate the problem with things like Furmark. The highest temperature I've seen with that is 70 and it runs fine. It is very well cooled by fans, so I doubt that the card is overheating.
I have a radeon hd 6850 graphics card which should be fine to play these games on high(not highest) settings. The problem occurs even on settings lower than the recommended ones for my pc. Any ideas on what might be the problem?
The case is a GIGABYTE GZ-KF03B Black SGCC ATX Mid Tower Computer Case. It was pretty cheap. I just installed a SickleFlow 120mm case fan on the side by the gpu. I'm also using a 90mm fan for exhaust near the cpu in the rear of the case.
The card hits 70C under stress testing benchmarks, but crashes have never occurred during tests like Kombustor or Furmark.