#2 - Oct. 26, 2010, 9:47 a.m.
Looks like they changed the email as well.
Let's get this buttoned up for you for the time being so they can't come back. I strongly suspect your email may be compromised as well. You'll want to make certain of both your system security - and that of your email account.
Right now, security is the main concern so they can't get back in. If they can....they WILL be back, that is very likely.
This sticky may be useful.
Account Recovery Form
http://forums.worldofwarcraft.com/thread.html?topicId=26859148968
You may also want to look into getting an authenticator for your account. It's no substitute for good security habits, but it will help keep them out of your WoW account.
Blizzard Store
http://us.blizzard.com/store/browse.xml?f=c:6
Mobile Authenticator
http://us.blizzard.com/support/article.xml?locale=en_US&articleId=26109