gtx 580 get's stuck at 3d clocks with "prefer maximum performance"

[er557]

I have enabled "prefer maximum performance" to troubleshoot some other issues;
Upon fresh install of the drivers the card clocks down normally when completely idle, although after some gaming and normal usage, the card is stuck in full 3d clocks ,fan @2k rpm, at all times. this is with drivers 285.38 and also now with 290.36.
That's in vista x64 , BTW.
Any solution or suggestions?
Thanks!
BTW, reboot or shut down didn't restore clocking down, only a new driver installation did. Haven't tried rebooting with the new drivers though.