I know this problem, why?
I had it on my laptop, caused by overheating during play.
Your pc might not be hot but the card itself just burned half of itself.
I sent mine to repair, luckily i had ensurance
I know this aint much of a help to you, but i guess thats it.Your pc must go thru the endless repair, or you can also buy the same card again or upgrade.I fail, i just read you latest comment, lolz.