Patch on Monday? Really??

This was a temporary issue that should now be resolved, Faestine. Try closing down the program and booting it back up using the Launcher.exe program located in the Worldofwarcraft directory.

Additional advice can be found in the following forum post in the Technical Support forum.

http://forums.worldofwarcraft.com/thread.html?topicId=20860801510&sid=1&pageNo=5#96

Quoted for convenience:

Q u o t e:

If you're getting a Failed to Apply Patch, Windows Vista or Windows 7 may not be permitting WoW to patch itself. Right-click on the World of Warcraft shortcut, and "Run as Administrator".

If you still can't connect, I would clear up any residual cache or connections, and power cycle the network:

1) Shut down your computer
2) Unplug the router and the modem
3) Wait for a minute, and then plug the modem back in, and let it fully power up until all of the lights are solid.
4) Plug in the router, and let it fully power up.
5) Boot up your computer, and try to log in.

The DNS cache may need to be cleared too: http://us.blizzard.com/support/article/flushdns