[rsj1]

I'm getting a mysql error on just one of my sites with this hack active (the error doesn't appear when it's disabled)

Database error in vBulletin 3.8.1:

Invalid SQL:

               SELECT
                       user.username, (user.options & 512) AS invisible, user.usergroupid,
                       session.userid, session.inforum, session.lastactivity, session.useragent,
                       IF(displaygroupid=0, user.usergroupid, displaygroupid) AS displaygroupid
               FROM session AS session
               LEFT JOIN user AS user ON(user.userid = session.userid)
               WHERE session.lastactivity >;

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 '' at line 7
Error Number  : 1064
Request Date  : Friday, March 13th 2009 @ 09:44:14 AM
Error Date    : Friday, March 13th 2009 @ 09:44:15 AM
Script        : http://(removed for privacy).com/forum/index.php
Referrer      :
IP Address    : (removed)
Username      : Ai
Classname     : vB_Database
MySQL Version : 5.0.67-community

It seems to be messing up the session data for some reason, but I cannot see how and do not have any other mods that effect that area...

Any suggestions? This hack works fine on all my other sites... all sites are running VB3.8.1 pl1, all sites use the same skin and all sites use similar hacks although there are extra hacks on this site it refuses to work on. They also all run from a dedicated server which only runs installations of VBulletin and Photopost