[Marco van Herwaarden]

I would ask advice over at vbulletin.com, but if i where you i would do the following:
- Contact your host, and ask them to check log files if someone from his ip had access to the server (doubt they will find)
- Make sure you got correct backup of your 306 database (yes i know you will be loosing data)
- Backup anything else you have on that server as long as you can 100% verify that it is unmodified.
- Ask your host to do a fresh reinstall of your server (you will loose everything!!) using the latest versions of all software (PHP4, MySQL3 (if you want MySQL4.0/4.1)). Make sure they also give you new passwords to your server.
- Reinstall a FRESH copy of vB 3.0.8
- Install your backup in a temporary database
- Perform the upgrade tasks to 308
- Create a new forum database
- Use Impex to transfer forum info from test to the new database.
- Change all admin.mod passwords. Make sure that your admins don't use easy passwords, and that they all have clean PC's (no keyloggers, trojans, etc..)
- Remove the old test database.
- Open your board again, if you want you can upgrade to 3.5Rc1 again.

The reason that you must go back to 3.0.6 backup is that there is no ImpEx for 3.5 yet.