Does it also do this at 3dmark06 loading screens (between tests). I've noticed a high pitch sound coming from my PC when displaying a high number of frames, sort of like signal noise? if that's what you can call it. I think it's disturbance from high frequency refresh rates, but I can't seem to find what's actually making hte noise. I don't think it's something to worry about really, but it's quite annoying sometimes :?
P.S I have an 8800 GTX, maybe someone else noticed this?