First, double check that your firewalls or security programs aren't blocking the game. By far this is the biggest reason for this problem. If they are good they should pop up once you attempt to attempt to connect again, so alt-tab out and see if one you forgot about shows up.

Beyond that there are some settings with ports that can occasionally get messed up. Also I suppose its possible if your college provides the internet in your dorm that they may block those ports or do any number of things that could prevent it from connecting (can you play any other games online). And while this may seem obvious, make sure you are putting your user name and password in correctly, remember its not necessarily the same as your impulse account.