wp 3.0 hacked?

I update the 3.0 version from 2.9.2 my admin’s password changed on me. I can’t log into my admin. So I changed the password from the phpmyadmin. I log back into the admin quickly using the newly created password. I looked through quickly to find the admin username, password, and email has been changed to something else. I’m thinking that someone is hacking my site. So I quickly deleted all the files to the site and reinstall the backup files of version 3.0. After reinstallation, the same thing happened. I was fed up with it thinking, “it might not be a hacker but the 3.0 version”. Lucky, I got a backup of 2.9.2 handy. I installed 2.9.2 and what do you know. Everything works fine just like before the update to the 3.0. My conclusion, no idea, is to stay away from this 3.0 version until someone figure out what went wrong.