PC Specs: Win 7 Ultimate 64 bit
CPU: AMD Phenom II X4 955
GPU: Sapphire Radeon HD5850
MoBo: MSI 870-c45
If you need more informations, just tell me and I'll give it to you.
I used to play the game with the visuals maxed out and didn't have this problem.
Now, I don't know what's the cause of the problem because Since the last time I played and had no problems at all I've updated my AMD Catalyst drive to the latest and the game also got a few updates.
My "problem" is that I have low FPS. It shouldn't be like this.I can't tell you the exact number of FPS but I think it's about 15 or something.

Please ignore my clumsy english and give me an Idea about how I could fix this.