Index: includes/menu.inc
===================================================================
RCS file: /cvs/drupal/drupal/includes/menu.inc,v
retrieving revision 1.415
diff -u -p -b -r1.415 menu.inc
--- includes/menu.inc	20 Oct 2010 00:47:43 -0000	1.415
+++ includes/menu.inc	21 Oct 2010 16:07:01 -0000
@@ -2151,6 +2151,12 @@ function theme_menu_local_tasks() {
 
 /**
  * Set (or get) the active menu for the current page - determines the active trail.
+ *
+ * @return
+ *   An array of menu machine names, in order of preference. The
+ *   'menu_default_active_menus' variable may be used to assert a menu order
+ *   different from the order of creation, or to prevent a particular menu from
+ *   being used at all in the active trail.
  */
 function menu_set_active_menu_names($menu_names = NULL) {
   $active = &drupal_static(__FUNCTION__);
@@ -2159,7 +2165,7 @@ function menu_set_active_menu_names($men
     $active = $menu_names;
   }
   elseif (!isset($active)) {
-    $active = variable_get('menu_default_active_menus', array_keys(menu_list_system_menus()));
+    $active = variable_get('menu_default_active_menus', array_keys(menu_get_menus()));
   }
   return $active;
 }
Index: modules/menu/menu.module
===================================================================
RCS file: /cvs/drupal/drupal/modules/menu/menu.module,v
retrieving revision 1.233
diff -u -p -b -r1.233 menu.module
--- modules/menu/menu.module	24 Sep 2010 00:37:43 -0000	1.233
+++ modules/menu/menu.module	21 Oct 2010 16:07:01 -0000
@@ -262,6 +262,15 @@ function menu_save($menu) {
 
   switch ($status) {
     case SAVED_NEW:
+      // Make sure the menu is present in the active menus variable so that its
+      // items may appear in the menu active trail.
+      // @see menu_set_active_menu_names()
+      $active_menus = variable_get('menu_default_active_menus', array_keys(menu_get_menus()));
+      if (!in_array($menu['menu_name'], $active_menus)) {
+        $active_menus[] = $menu['menu_name'];
+        variable_set('menu_default_active_menus', $active_menus);
+      }
+
       module_invoke_all('menu_insert', $menu);
       break;
 
@@ -299,6 +308,15 @@ function menu_delete($menu) {
   // Delete all links from the menu.
   menu_delete_links($menu['menu_name']);
 
+  // Remove menu from active menus variable.
+  $active_menus = variable_get('menu_default_active_menus', array_keys(menu_get_menus()));
+  foreach ($active_menus as $i => $menu_name) {
+    if ($menu['menu_name'] == $menu_name) {
+      unset($active_menus[$i]);
+      variable_set('menu_default_active_menus', $active_menus);
+    }
+  }
+
   // Delete the custom menu.
   db_delete('menu_custom')
     ->condition('menu_name', $menu['menu_name'])