Can you tell me what I'm doing wrong?

This is the error:

Database error in vBulletin: Invalid SQL: SELECT iconid, title FROM thread WHERE forumid= ORDER BY lastpost DESC LIMIT 1
mysql error: You have an error in your SQL syntax near 'ORDER BY lastpost DESC LIMIT 1' at line 1
mysql error number: 1064
Date: Friday 21st of September 2001 07:43:38 AM
Script: /forums/editpost.php
Referer: http://helpdesk.hostbet.com/forums/e...tpost&postid=5