Computer freezes up during gaming

Hey what's up, just built a new system about a week ago and all seemed well until I started using it for its intended purpose....gaming.

Turned on Bad Company and everything ran pretty good for about an hour or so when the screen froze up and the last sound heard kept repeating. Figured it was a game glitch so I restarted my PC and gave it another go only this time I had RealTemp, SIW and the MSI Afterburner (with logging enabled) running thinking that maybe my GPU was overheating. Again, it ran great for about 30 minutes this time before freezing up. I restarted and pulled up the log and saw that the temps for the GPU never went past 69c and the average GPU usage was around 80% give or take. Also, I've ran Prime95 several times on my PC and the temps never went above 55c so I know it isn't the CPU overheating. I can have my PC on for hours doing normal every day tasks and it's fine, no freeze ups, glitches or whatever. My thoughts are that my PSU isn't able to handle wattage needs and that it's shutting down. I have no way to prove this which is why I'm posting on here in the hopes that someone can help me fix the problem so I can play BF3 for hours on in when it comes out lol.

System specs are

Win7 Ultimate 64x
Cooler Master HAF X Tower
P8P67 PRO MOBO
x2 4Gb G.Skill 1600Mhz RAM
Corsair 750w PSU
Intel I7 2600K
64Gb Kingston SSD
1TB WD HDD
XSPC CPU water cooling


Any advice/help would be greatly appreciated.