Problem: Passwords Abruptly Stopped Working

[taylor_smith]

Hullo! I'm having a tricky problem with vBulletin 3.7.

My boss turned off Cloudflare on one of our servers to troubleshoot a problem. Additionally, last night we suddenly started seeing this message:

Database error in vBulletin 3.7.2:
Invalid SQL:
SELECT * FROM ipban 
where ip = ( & ((pow(2,`cidr`) - 1) << (32 - `cidr`))) 
and registration = 0
and (`expires` = 0 OR `expires` > 1329785877) 

ORDER BY cidr DESC;
MySQL Error   : You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '& ((pow(2,`cidr`) - 1) << (32 - `cidr`))) 
and registration = 0
and ' at line 2
Error Number  : 1064
Request Date  : Monday, February 20th 2012 @ 04:57:57 PM
Error Date    : Monday, February 20th 2012 @ 04:57:57 PM
Script        : http://vboards.stratics.com/search.php?do=getnew&exclude=63
Referrer      : 
IP Address    : 
Username      : Syrus
Classname     : vB_Database_MySQLi
MySQL Version : 5.0.51a-24+lenny4-log

Eventually, I was able to bring the site back up by deactivating a plugin called "Advanced IP Ban Management." This plugin has been installed for years. No idea why it suddenly borked out. Maybe something to do with Cloudflare?

After disabling the plugin, the site came back up, but now we have a new problem: no passwords work. No users can log in, no admins can log into the ACP, and no moderators can log in to perform moderator actions.

We have a couple of technical people, but they tend to be slow and/or unreliable. Does anyone have any idea what might have gone wrong or how we might fix it?