Better to have too many updates than never enough.

A good friend of mine in my guild had this exact same thing happen to him, his email was repeatedly hacked and his WoW account comprimised several times. Blizzard kept fixing it, but it was apparently a big hassle. He got an authenticator and a new email addy, no issues after that. I decided to grab one too a few months later after seeing what a mess a mistake like that could end up being.

Had this exact same issue earlier, ultimately an icebox download and a relog fixed it perfectly after some initial head-scratching, turns out my old WoW installation on a spare drive was messing me up. Glad it worked out for you too! This thread saved me some trouble.