well, dont know what all youve done, this is straight from the wow tech support board, and im sure you know this as well:
http://forums.worldofwarcraft.com/thread.html?topicId=10021039&sid=1
7. Error 131
The "Error 131" error message is usually caused by corrupt game files.
The first approach to resolving this error should always be the repair tool. The repair tool is located in the World of Warcraft folder called repair.exe. If you are unable to locate this file in the WoW folder it is available for download here: http://ftp.blizzard.com/pub/WoW/other/Repair.zip . Please use this tool, it will try to repair any corruption that exists, if it is unable to you may need to follow up with the next step.
The second step, as the repair tool will sometimes advise, is to reinstall World of Warcraft. Before reinstalling, be sure to uninstall WoW first by using the provided short-cut placed in WoWs Start Menu folder or by using the Add/Remove Programs tool in the Control Panel.
If you are still encountering this error please read our support page here:
http://us.blizzard.com/support/article.xml?articleId=21026
To begin troubleshooting this error we will have to see the complete error log. This error will have created a text file in the World of Warcraft\Errors folder. Please locate the most recent error file there and copy and paste the contents in a new thread below.
[ Post edited by Nickjs ]
Something may have gone wrong during the patch install.
Game experience may change during online play.