Have you checked to see if your processor or graphics card is overheating? (There's different ways to check this but I don't know your setup). You could put a window-type fan next to it and have a ton of air blowing on it as an easy experiment.
Have you tried defragging your hard drive?
Have you installed any other software since the last time it was running okay? If so, uninstall that software, reboot, and see if that fixes it.
I'm assuming you've already tried everything in this post:
http://www.mobclan.com/forums/upload/index...mp;#entry154136