When you get disconnected to the login screen you might as well kill the game. Trying to log back in straight away will only get you staring at the login screen with a full loading bar where you will have to kill the game anyways. Pretty annoying since the game is not entirely free of disconnects as it is.
I'm not sure if this happens for all computers and setups, but I know it's been happening to several guildies of mine. Logging over to another character does work normally, luckily.