I've been having this problem too since yesterday, in fact I'm unable to play now. The maintenance message alternated with an error.
I contacted right away the client service about it, and they said that problem can be caused by a load of things and they'd email me after finding a solution. Still waiting for the email of course.
The fact that now I see it's a common problem tells me for sure it's not a client-end problem.

Sigh, I just want to play.