Heh, I downloaded that last night also and had a blast with it, lol...
are you able to play singleplayer and have you EVER been successful at joining a multiplayer game or does the game always crash?
random ideas:
1) sp-1 installed?
2) create a new profile
3) keep trying to connect (to same and diff. servers)
4) if you see some warning about LANs when trying to connect, hit cancel...
just some things to get you started so we can get you back on the game grid!