So, guys, let's clarify: we're trying to track down a bug a person is exploiting to crash servers. Until we figure it out and issue a patch, you can assume the MS will be up and down as we enable it for testing and disable it after we're done.
In the meantime, if you want to play online, we suggest getting some friends together and playing a game by joining by IP manually. We'll figure it out eventually and turn the MS back on for good.