Have you checked your system for infections? I believe your subscriptions system is still infected or you still have some remaining identities from an infection.
This is the x00x Bot list.
http://www.zone-h.org/archive/notifier=x00x_BOT
Double check your system by using the best practices listed below.
Then please read the following two blog posts:
http://www.vbulletin.com/forum/blogs...ve-been-hacked
http://www.vbulletin.com/forum/blogs...vbulletin-site
Also please see these recent security announcements:
http://www.vbulletin.com/forum/forum...-1-vbulletin-5
http://www.vbulletin.com/forum/forum...d-all-versions