You should also check to see if your college is not blocking gaming ports ("MS Gaming Zone"). You may have been able to connect previously, but there could have been a change in policy or configuration at your school.
Well I can get into the lobby now, but I can't connect to a server...it just says "Joining game" for about thirty seconds, then says "Failed to connect to server."
Goodguy, please post what AV and/or firewall are you using.
Also, as Shiz said, it would be nice to know how did you fix this. The info might help someone else in the future
You'll have to uninstall McAfee completely and get a replacement (NOD32, Avira) or uninstall McAfee and reinstall it without the firewall component (the latter is not guaranteed to work though).
I HAVE FOUND THE ANSWERE. Ok i know im coming out of the blue here but you have to be an administrator. I tried using it on my kids account and i got the problem. But i ran it as an administrator and walla, it works. ^^ You may have something else wrong with yours though.