Random FPS dropping

Typical FPS for me is around 170-190....Randomly my FPS will drop to about 8.

Running Windows Vista Home Premium with AMD Phenom 9550 Quads/6GB RAM and a GeForce9100

when this happens I could be doing absolutely nothing and idling in game or with ACE in middle of a match destroying baddies.

and first off there are no viruses on my computer, no windows updates are being preformed, this happens with or without GameBooster running. There is nothing wrong with my computer at all, its only a year old, I built it myself, and it is running DOD security programs which do not affect the performance of the computer.

Is anyone else having these issues?? Ive met about 2-3 other people who say they get the same problem.