i have the same artifacts with my asus 660ti oc for past 6 months, it happen with SC2, WOW, but not diablo 3. I thought it was a drivers problem, so i keep upgrading the drivers each time nvidia have a new release but the artifacts keep coming back, then i went out to buy a asus 770 dcuii oc last week. no driver update or anything , the artifacts is gone, so i RMA my 660ti right the way, they call me to pick up a replacement card in 3rd working day but i think is a refurbish card. well i dont have time to try out the replacment 660ti yet. because the 770 is working nicely. if you are not overclocking your card or the max temp of your card is under 90 you probably need rma your card.