MW2 - Multiplayer doesn't start - Black screen

Hi,
I really need help, I'm experiencing an annoying issue with Modern Warfare 2 Multiplayer: when I launch the game, a black screen appears with the mouse which I can move, but the game doesn't start, and the only way to continue is to kill the iw4mp.exe process...

Please, could someone tell me how to fix this problem?

My laptop:
Video Card: NVIDIA GeForce Go 7600
RAM: 2 GB
CPU: Intel Core 2 CPU @1.73 Ghz, 1.73 Ghz
Windows 7

I could play fine COD 4 MP and SP and of course I can play the SP of MW2... help!!!

(I've tried a lot of things:
Disabled firewall, disabled all the services, updated all the drivers, and run the game in compatibility mode with XP service pack 3, but nothing, I can't launch the MP.... please help me)