I have this issue as well, and I also had another graphical issue. As a result of the graphical issue, I borrowed a friends video card to see if that fixed the graphical problem, which it didn’t. (Turned out to be an unstable CPU overclock on my part.)
Any ways, pertaining to this issue, once I switched out my AMD HD 4870 to my friends 6870, I haven’t had this sound problem. I had to give him back his card yesterday as he was selling it on ebay, and today I played with my old 4870 and the issue happened again.
Now when it comes to sound cards, I am actually using a USB DAC, and not an onboard card, so not sure if that says anything. But people, try changing graphics cards if that option is available to you. If you do not have the issue, it COULD be GPU related then.
My 2 cents and experiences.