Index: tasklist.c
===================================================================
--- tasklist.c	(révision 1357)
+++ tasklist.c	(copie de travail)
@@ -2203,6 +2203,10 @@ wnck_tasklist_update_lists (WnckTasklist
 	  /* Class group */
 
 	  class_group = wnck_window_get_class_group (win);
+          /* don't group windows if they do not belong to any class */
+          if (strcmp (wnck_class_group_get_res_class (class_group), "") != 0)
+            continue;
+
 	  class_group_task = g_hash_table_lookup (tasklist->priv->class_group_hash, class_group);
 
 	  if (class_group_task == NULL)
