Recently im having huge fps drop at wall street map, i dont know why. Usually i play with 20-40 fps at high settings disabled motion blur + clear nanovision edit. But when i begin wallstreet it drops to 3-5 fps, this is my comp spec can admins or somebody else help me out in this?

Windows 7 64 bit

E8400 3.0 ghz
MSI g41m p33 combo
palit 8800 gt
4 gb gskill 1333 mhz cl7