Hate leaving the game as per Chile's fix. I've found that if you simply keep maps up to date, you won't have this problem.
A duplicate Q port simply means you're still logged to the game server, which happens when you crash on a map changeover. Your system receives an instruction to load the new map, and your computer doesn't have it. So your computer returns a message to the server to the effect that the client machine doesn't have the map, and in the case of this game, the game crashes. But, even after the crash, you're still logged into the game server for that map and can't reconnect because the server thinks you're already connected.
This error will go away when the map you failed on runs its course on the server, and the server refreshes. So, either wait a few minutes and you'll be able to reconnect, or, keep your maps updated using the downloader.