"- The GPU automatically down clocks because it is idle and conserves power"
And off-topic, get a new CPU, Starcrat 2 will poop on that one.
I noticed a steep drop in FPS last night in SC2, got down to 9 at one point. Will be popping in a Q6600 and oc to 3.0Ghz. Hopefully that helps.
Thanks for the quick replies Benski and Dipankar2007i!