Have you re-uploaded your files (namely the index)? A lot of times, it's simply a matter of having your index file replaced with the hacker's 'scary' message. Moved to Security and Legal.
Sorry this has happened to you! If you have trouble fixing the damage, try doing a search for warezd or C0D3D + hacked, there are probably many other people cleaning up the same mess. Keep us posted on how it works out.
I looked at the page source of your website and the index is completely replaced with the hacker's. Do you have a file backup?
You also might want to read the article Wayne posted to prevent this from happening. I hope you have a file backup and if they droped your tables a database backups.
Here is an article on how to recover a hacked/defaced vBulletin site: Tutorial Recovering a Hacked vBulletin Forum - vBCodex p.s. If this is an inappropriate link, please let me know.
my site was hacked twice and the second time i lost everything so i feel your pain. I hope you get everything sorted soon.
its always best to upgrade to the latest vBulletin ASAP ...and also please don't use remember me option in firefox browser...there are several tools which can steal cookies from browser...