I got the same error a few times. I just kept restarting client until it let me get past the Start screen and let me load my characters. The only sad thing is all worlds are full now. I haven't been able to play for a few days.

Out of curiosity, anyone know why SE doesn't have a que so people can wait in line to login instead of spamming LOG IN button. I know they have one but it rarely ever shows up and when it does and it is my turn to log in it says World is Full...isn't that why I am in line..?