I'm having this issue as well. 1. Earlier, while the PvP server was down, I transferred my old characters from Nostalrius to my new Elysium account (I only had characters on the PvP server).
2. I'm able to log into and play the new character I created on the PvE realm while the PvP server was down; however, once I select the PvP realm (which shows no # of characters in-game), I'm automatically disconnected and then I get immediately "Disconnected from Server" when attempting to log in again.
3. I must then delete my WDB/Config.wtf files and re-open the game to log in and select the PvE server. If I select the PvP server, the cycle continues. Extra info: I've confirmed my old Nostalrius characters appear on the character list found through the Elysium website: account manager.
Update: I was able to log in successfully on the PvP realm by dismissing the error and logging in over and over, about 6 times. It hung on character creation seemingly until I tabbed out. When I tabbed back in, it had loaded all of my characters. Then the same thing happened with a full loading bar on the Kalimdor loading screen. I tabbed out and back in and it had loaded the world successfully.