I'm not highly experienced with this stuff, but I think I may have had this problem too. If you are running an AMD card, then it may be the latest driver. I know that was causing a problem for me a few weeks ago, however like I said, that was a while ago, so it may not apply anymore. I would try turning off anti aliasing, because that's what I was told to do and from what I remember, it seemed to do the trick. Turn it off in the game settings and on your card too through Catalyst or whatever NVidia has.