Artifacts and can't figure out why.

Hey guys and gals,

I am completely stumped with this problem so I've decided to seek some advice from you guys.

Story:

Around a month ago I purchased a EVGA GTX 590, after installation on idle the computer would work fine, but during load (i.e. gaming or stress tests involving GPU) the computer would shut down, I isolated this problem to the generic PSU I had, and had it replaced with a Corsair HX850W.

After that, everything worked fine for about a week, and then artifacts began to appear in different games I played. I don't have any screen shots with me at the moment, but this video is a perfect example with the same problem I have.

Battlefield Bad Company 2 -
League of Legends -
And I also get similar artifacts in Eve Online.

Now the weird part comes when I tried to do stress test (not games) to see if it gives the same problem.
- I have tried Furmark, Unengine, 3dMark and all run fine with no artifacts.
- I have also tried memtest to see if it might be ram problem but it passes with over 32 hours of run time.
- I have also tried Prime95 and OCCT on my CPU and it passes fine with +15hours on each.

I have also tried multiple drivers, both official and beta from Nvidia, first with the driver sweeper + safe mode option, then with a fresh install each time (yes...fresh install just for driver -.-) but doesn't fix the problem.

So now I'm completely stumped on whats causing the problem. Listed are my computer specs below.

Intel i7 970 (Stock, no OC)
Asus Rampage III Formula
Corsair Vengeance 3x4GB 1600mhz (Overclocked to 1600mhz @ 1.65v b/c board doesn't natively support 1600)
EVGA GTX 590
D-Link wifi card
Corsair HX850W PSU
2 x 1TB WD Greens
1 x 2TB WD Green
1 x DVD Drive
2 x Intel 320 120GB SSD in Raid 0 (For OS)