DB error when viewing PMs

[1QuickSI]

Just started happening...
Any ideas?

Database error in vBulletin 3.7.2:
Invalid SQL:
SELECT
    *
    FROM moderator
    WHERE forumid= AND userid=5;
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 'AND userid=5' at line 4
Error Number  : 1064
Request Date  : Wednesday, August 13th 2008 @ 10:35:12 AM
Error Date    : Wednesday, August 13th 2008 @ 10:35:13 AM
Script        : [URL]http://www.domainname.com/forums/private.php?do=showpm&pmid=20[/URL]
Referrer      : [URL]http://www.domainname.com/forums/private.php[/URL]
IP Address    : 208.xxx.xxx.xxx
Username      : Steven
Classname     : vB_Database
MySQL Version : 4.1.22-standard

[Steve Machol]

Invalid SQL errors are almost always related to modified code. To troubleshoot this, the first thing you need to do is remove any third-party hacks or plugins, then see if you still have this problem.

If so, reupload all the original vB non-image files (except install.php). Make sure you upload these in ASCII format and overwrite the ones on the server.

Next, create a new style and choose no parent style. This will force it to use the default templates. Finally empty your browser cache, close all browser windows then try again. Make sure you change to the new style and view your forums with it. Do you have the same problem?