VIdeo Card issue... I think. Help Please!

Hello all, I have been experiencing some issues on a new system I built. Everything posts fine, bootup is fast with no problems, windows runs fine... system will pass prime 95 for 10 hours and Intel Burn Test 10 cycles with no errors/crashes and keeping processor temps below 65C. However whenever I play a graphically demanding game... Crysis/Civ 5/BFBC2 after about 10-15 minutes the games go to a black screen and do not recover, however I am able to ctr-alt-del and end the programs manually after which my system returns to windows without issue. The following are my system specs:

intel i5 2500k (was running at 4.5ghz but have reduced it to stock to troubleshoot this issue)
Asus P67 Sabertooth motherboard
8gigs G.skill ripjaw at 1600mhz
WD Caviar Black 1TB HD
2x EVGA GTX 460 FTW EE in SLI (using most recent nvidia drivers)
24x dvd-rw
Coolermaster 690 Case
Corsair 750HX PSU
Corsair H70 CPU cooling system
Windows 7 64 bit

My case has 1 front mounted 120mm intake fan, 1 120mm top intake fan (mounted all the way at the front of the case blowing air down the drives) 1 120mm side intake fan blowing cool air directly on the GTX 460's. For exhaust the case has the Corsair H70 with 2x120mm fans in push pull config as well as the dual gtx460's which are external exhaust.

I can't figure out what the problem is, please help!

Look at your GPU temps during gaming...I suspect that your GPU' are overheating or possibly pulling more power than your PSU can deliver...Try running only one GPU and see if you still have the crash in games.