Green Dot on some frame

Hello, iam writing for my friend who started the game and is having some green dot flashing here and there during some fram, game run at +/- 40 fps, sometimes he wont have any for a few mins sometimes it will keep poping here and there moving around the screen.


He got a G-force 660 gtx, latest driver. Steam version of the game, tryed both Dx 9 &11 and the problem persist. He say his 3Dcard is cool and not overheating.

http://imgur.com/a/kjVT7

http://imgur.com/a/kjVT7 <= screen

Any idea ?
Thx in advance for him.