System Freezes Under Load

[Codex]

Hi All,

Recently I built the following system, some parts were from my previous build namely HDD, Case and PSU.

New Parts:
Intel Core i7 3930K @ 3.2GHz
G.Skill 16GB (4x4GB) DDR3 Kit, PC-12800 (1600Mhz), RipjawsZ, 9-9-9-24-2N
Asus Rampage IV Formula, X79
Gigabyte 7970 3GB x 2 (Crossfired) Cat 12.8
3 x 23” Samsung LCDs (5760x1080)

Existing Parts:
2 x WD 500GB HDD
1 x OCZ Agility 3 120GB
1 x OCZ Agility 3 240GB
Thermal Take tough power 850W
Raven II case

OS Win 7 64bit Pro

Now the issue I have is the system locks during gaming and it's with all games, so it's when it's under load. Usually after about 15 min or so. To get it back I have to physically cut the power, I can't even use the reset boutton on the case.

With general apps like Firefox for example I'm getting corruptions in the text and then a black viewing area, with IE9 I'm only getting corrupted text.

Now I havn't overclocked anything, I'm still learning the motherboards various options but I've set the overall profile to default.

Now with 2 x HDDs, 2 x SSDs, 2 x GPUs, an i7 3930k and 4 x case fans running is my 850W PSU enough? Is this overheating? Is this a memory issue?