#2 - Sept. 4, 2010, 9:59 p.m.
I am happy to hear you have an authenticator attached to the account. I am guessing if you did not, you would be posting here for another reason entirely. :(
I was able to review the account concerning the passwords being changed without you receiving any confirmation of such. It appears as though a foreign party has the information necessary to perform the password retrieval process. With that knowledge, and the fact that the passwords for Battle.net and your email address were the same, they were able to receive the notification before you had any idea as to what was occurring.
In cases like this it is recommended that you update the email address associated with the Battle.net account. This new email address becomes the account name, therefore blocking the individuals from successfully resetting the password.
Definitely, rescan the computer, but this time scan with the game running in the background. Sometimes malicious programs will not “activate” until the game begins. We have several programs on our website that are free, or at least free to try that you may have success with. You may find this information here:
Account and Computer Security http://us.blizzard.com/support/article/30794 (specifically #3 and #4)
Good luck!