Forum Database error in vBulletin 4.2.0
 

For months, I've been getting a Database error email for 4.2 PL3.

I have repaired/optimized tables and emptied session cache in phpmyadmin. Here is what the emails states...

Code:
Database error in vBulletin 4.2.0:

Invalid SQL:

SELECT data, expires, locktime, serialized
FROM cache
WHERE cacheid = '';

MySQL Error :
Error Number :
Request Date : Tuesday, February 19th 2013 @ 11:26:00 PM
Error Date : Tuesday, February 19th 2013 @ 11:26:00 PM
Script : http://www.mysite.com/external.php?type=RSS2&forumids=11
Referrer :
IP Address : XXXXXXXXXXXX
Username : Unregistered
Classname : vB_Database
MySQL Version :