[Troubleshooting] Freezing during gaming

Specs:

i3 2120 (IDLE: 30-36 *C, LOAD: 59-65 *C) Gigabyte Radeon 6770 1GB (IDLE: 26-32 *C, LOAD: 45-52 *C) Mushkin Stilleto 8GB, 2 4GB sticks Seagate Barracuda 7200RPM 160gb (IDLE: 28 C, LOAD: 35C) ULTRA 650w 80% efficency PSU Cooler Master Elite 371 Case (all of these temps recorded by CPUID

This problem is really weird. Less demanding games such as Minecraft and Left for Dead 2, Torchlight II work just fine at about 45 *C.

On the other hand, when I try to play something like Just Cause 2 or Starcraft 2, the screen will go black/display vertical lines.

When that happens, I am forced to either one: Restart my PC (the audio in the game continues for a few seconds, then freezes and repeats annoyingly) or it brings me to the desktop and says "AMD driver has crashed and recovered" (or something along those lines).

I'm totally stumped. This problem occurs randomly, sometimes I can be 30 minutes in and it'll happen, or I could be 1 minute in and it could happen. Also, my GPU NEVER goes over 50 while gaming and it still crashes, on the other hand when I'm F@H and my GPU is @ 51*C it will run just fine. So I guess temperature isn't the issue here. I have tried using a different 6 pin connector, reseating the graphics card and installing the latest drivers from the AMD website. I've had this computer for 1 month and twelve days now.

Please help :(