I think the way to fix it is to get to the screen where it says you have to re-authenticate and press the log out thing. This seemed to allow me to log on. Maybe the client thinks you're already logged on since you didn't exit the game properly (clicking the "x" to logout, instead of just closing the application). I don't know, let me know if this works for you guys. I've tried many things to get it working and certain things seem to make it work again, but then when I try it again, it doesn't work... So it could just be random.