PSU flickering leads to GPU failure

Here is a video of what happens:

Whenever I try to game longer than 10 minutes on this rig I JUST built, my PSU starts flickering like a strobe light and then my computer freezes. Sometimes it will display a random color though out the whole screen, or just go black. I have checked all my temperatures when this occurs and they are all well below average. I have ALL the latest drivers/windows updates.

In this case like many others, my screen goes black for a few seconds but then recoveres, only to have terrible FPS (I usually get 80+).

System Specs:

CPU: Intel Core i7-3820 Sandy Bridge-E 3.6GHz (LGA 2011)

GPU: EVGA GeForce GTX 660 3GB (Factory SuperClocked)

HDD: Western Digital WD Blue 1TB 7200 RPM

PSU: Rosewill Xtreme Series RX850-S-B 850W

MB: ASRock X79 Extreme6 LGA 2011

RAM: G.SKILL Ripjaws X Series 8GB (2 x 4GB) 240-Pin DDR3

OS: Windows 7 Professional x32

What should I do?

I dunno about the rest, but don't you have to populate all 4 RAM slots?

And seriously, Win7 32 bit? Or was that a mistake..

I was just trying a different Os. and no, you do not.

You are correct, good sir. For some reason I was thinking about troubleshooting with some Dell guy .. my mistake.