Please help me. I don't know what is wrong. In single player my frame rate drops from time to time and renders the game unplayable. Can i do something to fix this ? I tried every graphic settings available but to no avail. On high details i get over 60fps (constant) but suddenly the frames are dropping the game is all slugish. I get the same thing on low details.
What can i do to fix this? Is there anybody else experiencing this problem ?

probleme look like cpu , whats ur cpu and how many ram u have too

Check your temp's, tell us your hardware and try disabling VSYNC.