Possible hacking attempt?

[HMBeaty]

I'm not sure if anyone else has had these errors come across, but this is the 2nd one I've got in 2 months.

  Database error in vBulletin 4.2.0:
   
  Invalid SQL:
  SHOW CREATE TABLE `vb_taggregate_temp_1339494960`;
   
  MySQL Error   : Table 'vb_taggregate_temp_1339494960' doesn't exist
  Error Number  : 1146
  Request Date  : Tuesday, June 12th 2012 @ 01:20:32 PM
  Error Date    : Tuesday, June 12th 2012 @ 01:20:49 PM
  Script        : http://www.usmilitarylife.com/cron.php?rand=1339521626
  Referrer      : http://www.usmilitarylife.com/forum.php?styleid=7
  IP Address    : xx.xxx.xxx.xxx
  Username      : Unregistered
  Classname     : vB_Database
  MySQL Version :

I've searched plugins and can't find anything relating to this error, and I've also searched files with nothing relating to this error.

Any ideas?