Hmmm a couple of things to try.
go to C:\Program Files\World Of Warcraft, or wherever you have WoW installed.
In this folder delete the
Cache
WTF
Interface
folders, it wont mess up your wow installation, all's it will do is delete any addons you have, the folders are remade the next time you start wow
Another thing to try is still in your directory you have WoW installed under run the
Repair utility this will repair any damaged files you may have.
Hopefully it's just a one off (or two in your case

)
Hope this helps.