Database Error Question

[hobbybox]

Im getting the following database error many, many times a day - however nothing on my site is not working correctly. Does anyone have any idea where I can find what is causing this problem?

Database error in vBulletin 3.8.1:

Invalid SQL:

			UPDATE user AS user 
			SET user.ppuploads =
			(
				SELECT COUNT(userid)
				FROM pp_photos
				WHERE user.userid = userid
			);;

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 'SELECT COUNT(userid)
				FROM pp_photos
				WHERE user.userid
Error Number  : 1064
Request Date  : Wednesday, March 18th 2009 @ 09:12:45 AM
Error Date    : Wednesday, March 18th 2009 @ 09:12:45 AM