This isn't really a bug as it happens every time there is major congestion due to too many logins both concurrently and attempted. More or less, it is the game telling you "I have too many trying to do too much at one time, I don't have time to deal with you!"

Sad that SE didn't think about this when they announced the expansion pack, knew their max capacities on servers, and active accounts with characters higher than lvl 20.