Do you have phpmyadmin?
If so, first to go the admincp -> users -> search for users -> xantrix and then at the top you'll see User: Xantrix (id:XX)
Write that number down, then go into your phpmyadmin and check out the useractivation table
browse it and see if there is multipe entries for that userid.
Not sure how it could have happened, but that's the table this hack gets it's info from as it's the one I clear out when I reload my test site.