Problems in FPS after a while playing

[FAE_Boquerón]

Same graphic, same problem.

Game runs fine (50-30 fps) but after 20 m of continous play, start suttering all the time. Frames goes up and down every second, if you look at gpu work at afterburner, it looks like close peaks when before it was almost 100 full time. I will try new drivers, Ill tell.

I5 2500k, nvidia560ti 9.18.13.1422