My brother has a pretty sweet rig:

i5-2500 watercool oc'd to 4.8ghz
8gb ddr3 ram watercool oc'd
Some SSDs
Windows 7
Radeon Sapphire 6770

But while we were playing last night his game kept severely stuttering to the point that it would just black out for 3-5 seconds every 20 seconds or so. Is this a known error? I can try to get on his computer when he wakes up and post a dxdiag if it would help. He has all his drivers up to date.