Long story short... server is full. Just keep on spamming enter when it falls back to the log-in splash screen with the UFP logo and you'll most likely get in within 5-10 mins, I know that's what I did.
Actually, you only need to hit enter twice on that screen.
i am getting it too, there is no info on why its happening today and no thats not what the problem is, when its full it says the server is busy, this one is the same error we get during closed beta inbetween tests.
i just started getting this as well.. and no way is the server full this time of day.
I guess they have taken the logon servers down, maybe for a new patch the main servers might go down soon as well..
Okay, so maybe that may be true, but JUST now, for giggles, I tried to login. I got in on my first shot so i PURPOSELY logged out. Try to log in and yes, did get that error message, 18 seconds later and 2 re-attempts and I was able to login...