2500k video issue? or user error?

So I just built my new system and I'm loving it. I'm running the 2500k with a GeForce GTX570 at 1920x1080. Within the first day or two i noticed when running black ops, while video was playing and occasionally while simply playing the game the computer would hesitate and emit a quick buzz noise. The hesitation has also occurred when just on my desktop. Any idea of possible remedies? I dropped AA down from 8x to 4x in black ops and that seemed to improve things a bit for the game. I thought that this system should be able to run black ops on full without a problem....