Same symptoms happened with me although mine was acompanied by a spinning scratching sound. Swapped the graphics card and it's no longer a problem.
In my case there was a sticker nvidia puts on top of their Quadro card's fan that appears to have melted and moved due to heat stopping the fan from turning which explains the scratching.
Thanks for all your replies. Just a quick question,does anyone know if you replace the stock cooler on your graphics card with bettter one,does that effect the cards warranty?
i would assume so