Index: lib.php
===================================================================
--- lib.php	(revision 402)
+++ lib.php	(working copy)
@@ -3787,7 +3787,7 @@
 
     $sql = "SELECT 'x'
               FROM {$CFG->prefix}forum_discussions d, {$CFG->prefix}forum_posts p
-             WHERE d.forum = $forumid AND p.discussion = d.id AND p.parent = 0";
+             WHERE d.forum = $forumid AND p.discussion = d.id AND p.parent = 0 and p.userid = $userid";
 
     return record_exists_sql($sql);
 }