When i'm shootin, with any weapon, just when i press the mouse botton and the weapon fire sounds, gets lag, like a screenshot, an horrible blink like 5 or 3 frames per second. And I know that are a lot of people who have the same problem. There is even a video with this problem ! http://www.youtube.com/watch?v=HPUQtoNqc6s
Normaly in game single player I get 65 - 110 fps( the problem doesnt happen in single player), and in multiplayer without shooting I get 60 - 90 fps.

Windows 7 - 32 bit !

My Pc>
1024-768 resolution
Core2 Duo E8500 3.3 GHZ
4 GB RAM
NVIDIA GTS 250

The GPU is not hot, it stays like 60o c





http://www.youtube.com/watch?v=HPUQtoNqc6s