error trouble

[salata]

Database error in vBulletin 3.5.4:

Invalid SQL:

	SELECT username as un, field15 FROM userfield uf, user u WHERE 
u.userid = uf.userid and
uf.userid IN (,575);

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 '575)' at line 3
Error Number : 1064
Date         : Tuesday, September 18th 2007 @ 10:36:38 AM
Script       : http://xxx.com/forums/index.php
Referrer     : http://xxx.com/forums/admincp/index.php?do=head
IP Address   : x.x.x.x
Username     : Salata

can someone tell me where this error is located? it pops up randomly