im having the exact same problem in the underworld sever. mostly in weekends between 19:00 to 00:00 PM local time (i live in israel) i simply cant get the game working.
im entering the game and can run around freely but no one moves and i cant activate skills and after few minutes it sends me back to the log in screen with error 7.
btw im lvling 5 characters at once and they are all in the starting zones. (mainly because of error 7)