I've had the same problem for a long time, after a while the screen would go blue with black vertical lines and then the audio would cop out after so many seconds later. I finally replaced everything in my computer including HD and OS, but I used the same graphics card.... and what do you know, same problem.

I guess the XFX Radeon HD 6850 will have to get replaced. Oh and guess what? That was the second card I had from XFX that did that. The other was an earlier model.

Live and learn.