Getting Database Error

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Database error in vBulletin 4.0.0 Beta 4:

Invalid SQL:

		SELECT user.avatarid, user.avatarrevision, avatarpath, NOT ISNULL(customavatar.userid) AS hascustom, customavatar.dateline,
			customavatar.width, customavatar.height, customavatar.width_thumb, customavatar.height_thumb
		FROM user AS user
		LEFT JOIN avatar AS avatar ON avatar.avatarid = user.avatarid
		LEFT JOIN customavatar AS customavatar ON customavatar.userid = user.userid
		WHERE user.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 '' at line 6
Error Number  : 1064
Request Date  : Tuesday, December 1st 2009 @ 05:27:35 AM
Error Date    : Tuesday, December 1st 2009 @ 05:27:35 AM
Script        : http://myforum/testforum/
Referrer      : 
IP Address    : 
Username      : Diljit
Classname     : vB_Database
MySQL Version : 5.0.67-community

can anyone help me