Why does COD: Black Ops run slow on my pc ?

I have a Nvidia 340 gt graphics card, i know this isn't great but it should be good enough. I have a constant fps of 85 - 95 which is pretty good but the game still feels sluggish. Aiming seems to be slightly delayed as if my fps was 40, not at all like mw2. Is this just the game engine in black ops or is there any way i can fix this ? Thanks a lot to any1 that can help.