Hey all, at the time of post the wow updater is down, at least in my corner of the world. I went to a third party site where i downloaded it from. Did a virus scan with zone alarm and found no malware. Logged into my account and everything works. I will post the link below, just look down the center column on the webpage and you will see links to the mirror sites. Pick the one with the lowers wait time. A window will open, then you just have to wait a few minutes to gain access to the server. Once i had access (4 min) it took me about 1 minute to download and install.

http://www.atomicgamer.com/file.php?id=78638#

this seems to be a pretty common issue today, i too had this problem.
i read a tip on wow.com, just close your launcher and try again, worked first try after that for me, but may take a few tries.