Maximum PC

Hi all, wondering if someone can help me with this issue I'm having.

When Playing two different games (Dishonored, and Borderlands 2), within 30mins to an hour I suddenly lose my video signal to the monitor. There is still sound (like the game is still running), for 5-10 seconds, but then that stops and sounds like it locks up (studdering sound). The computers fans still run, but everything else is unresponsive. I have to disconnect power to reboot.

I checked the usual suspects. PSU is fairly new, reseated all my cards, and memory, even rolled back my video drivers to 12.6. Still nothing helps. The odd part is i can run BF3/Civ5/GW2 (on highest settings) for hours on end, with no issue. It seems only those two games are affected (haven't tried Borderlands 1 yet, but am still currently downloading).

If anyone can help me with some ideas, it would be greatly appreciated, 'cause I'm stumped. Thanks in advance.

My system:
Win7 (64)
8gb ram
Asus radeon 7950 (stock)
i7 2600k (stock)
creative x-fi

It may be a heat issue. Try taking the side of the pc off, point a house fan at the opening and run the offending apps, if the apps run you know you have a heat issue. Are your apps fully patched?

Nasty

Also try getting the latest driver, and see if that helps. http://support.amd.com/us/gpudownload/windows/Pages/radeonaiw_vista64.aspx

I have checked temps running Dishonored vs. BF3. BF3 runs a little hotter, but still not too high. I still can play BF3 continusly, and yet only get 30mins (at most) playing Dishonored before this problem comes up. I do notice my temp2 on Speedfan shows around 50*C-60*C, but I've read that this is in error.

I am now running 12.8 drivers for my Gfx card, still no change.

...any thoughts?