#0 - April 30, 2008, 7:54 a.m.
Blizzard Post
Howdy, folks.

Nickjs all the way over on the Technical Support Forum has written up an excellent guide on how to resolve the immediate disconnection issue created by the Arena Tournament realms. Because we have been receiving numerous reports of this here on the Customer Service Forum we have decided to mimic his post here.

Q u o t e:
There is currently an issue where some players are now being disconnected immediately after logging in to the game. We have found this to be related to the Tournament Realms having been selected as their default realm due to a bug. This is slated to be fixed in a future patch but for those who are affected by this now, manually changing your realm under the Config.wtf game file has resolved the issue for many players experiencing it. Instructions can be found below:

1. Completely exit out of the game.
2. Open the World of Warcraft folder on your hard drive (Default Folder: C:\Program Files\World of Warcraft).
3. Open the WTF folder.
4. Open the Config.wtf file using a text editor, like WordPad.

Locate the line:

SET realmName "Realm Name"

Change this to: SET realmName "Your Realm"
-Example: SET realmName "Silver Hand"

Save the file and test the game out again. If you are using Windows Vista, please also check for the same Config.wtf file in the following directory (Please make sure hidden files/folders are being shown under your folder options. At the Windows Explorer window select Tools -> Folder Options and select this option under the View tab):
C:\Users\<your windows account name>\AppData\Local\VirtualStore\Program Files\World of Warcraft

Simply deleting the Config.wtf has also resolved this issue. If manually changing the realm does not resolve this specific login issue, please try completely deleting the file. If the issue still persists or the issue is not related to the Tournament Realms having been selected, please create a new thread for further assistance.

http://forums.worldofwarcraft.com/thread.html?topicId=5720532428&sid=1