Back when we first migrated these forums from PunBB, Thrillho worked some of his magic and hacked up the login script to accept the hashed passwords from the old installation. This was somewhat of a temporary fix however and when I upgraded to the latest vBulletin release last night, I undid the hack.

So, if you are a current registered user of these forums, you will need to complete a full password recovery operation. This is the only method which vBulletin endorses for converting imported passwords to those compatible with its software. Anyone who registers an account at a time after this news post, does not need to recover their password. If you have any issues, please contact a member of the administration through the link in the board footer (do not register a dummy account) and provide your username and e-mail address for verification.

I'm sorry for any inconvenience this may impose, but it's a necessity.

TL;DR: Recover your forums password you lazy bum.