I have the same problem as zekkecraft does. My SP is working as intended, I can start the game, do missions... But when I want to play MP, it starts and then the whole application crashes. "The application has stopped working." I am really clueless, I have latest DirectX, GPU drivers
, game patch and it is enabled in Windows Firewall.
When I had Win XP on this same computer, CoD 2 was working without problems, but other games did not. So I choosed to install other OS and I have chosen Win 7. Now the other games work but CoD 2 doesn't. I am even trying to run it with Win XP SP3 compatibility.