Index: chatroom/chatroom.module
===================================================================
RCS file: /cvs/drupal-contrib/contributions/modules/chatroom/chatroom.module,v
retrieving revision 1.6
diff -u -r1.6 chatroom.module
--- chatroom/chatroom.module	28 Jun 2006 16:16:59 -0000	1.6
+++ chatroom/chatroom.module	29 Jun 2006 14:18:08 -0000
@@ -446,11 +446,17 @@
     chatroom_update_online_time($chat_id, $user->uid, $session_id);
   }
   else {
-    db_query("INSERT INTO {chatroom_online_list} (ccid, uid, session_id, guest_id, modified) 
-                  SELECT %d, %d, '%s', COALESCE(MAX(guest_id) + 1, 1), UNIX_TIMESTAMP()
-                  FROM   {chatroom_online_list} 
-                  WHERE  ccid = %d",
-              $chat_id, $user->uid, $session_id, $chat_id);
+    db_lock_table('chatroom_online_list');
+    $result = db_query("SELECT COALESCE(MAX(guest_id) + 1, 1) 
+                        FROM {chatroom_online_list}
+                        WHERE  ccid = %d", 
+                        $chat_id);              
+    if ($result && db_num_rows($result)) {          
+      db_query("INSERT INTO {chatroom_online_list} (ccid, uid, session_id, guest_id, modified) 
+                VALUES (%d, %d, '%s', %d, UNIX_TIMESTAMP())",
+                $chat_id, $user->uid, $session_id, db_result($result));
+    }
+    db_unlock_table('chatroom_online_list');
   }
 }