Getting 1000s of errors in mails!

[penmai.com]

Hi,
Getting the following error in mails. Let me know how to resolve it.

Database error in vBulletin 4.2.2:

Invalid SQL:

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

MySQL Error :
Error Number :
Request Date : Monday, December 8th 2014 @ 09:52:34 AM
Error Date : Monday, December 8th 2014 @ 09:52:34 AM
Script : http://www.penmai.com/forums/externa...p;forumids=298
Referrer :
IP Address : xxxxxxxxxx
Username : Unregistered
Classname : vB_Database
MySQL Version :

I tried disabling all adons and tried still got the error.