Try reading around the forums first, this should be placed in the help board so you're good, but where there are already posts questioning the same thing.
I will repeat what I stated there. The server is having a little hiccup, not allowing users to log in. This is because it seems after the server hits a certain number at this time approximately every night, it can no longer handle the influx of players and begins going down.
This problem will be resolved soon, as the staff are working on it. Until then, the server will restart itself in a bit, allowing people to get back on.
