I got hit with this lastnight. When I woke up, I was able to log in just fine. So i thought it was fixed. My MISTAKE cause when i changed to a alt, I realized I couldnt swtich between characters without saying the connection to the data server was lost. Then pretty soon it wouldn't even load the data server and started throwing me the Lobby server error.

I disabled my internet on my PC and re-enabled it again hoping it would fetch a new IP address after doing that I was able to log into my main again. Not saying its going to fix the issue. but it might allow you to go on the toon your wanting to play.