Index: includes/menu.inc
===================================================================
RCS file: /cvs/drupal/drupal/includes/menu.inc,v
retrieving revision 1.317
diff -u -p -r1.317 menu.inc
--- includes/menu.inc	2 Apr 2009 03:40:05 -0000	1.317
+++ includes/menu.inc	2 Apr 2009 14:56:34 -0000
@@ -1832,24 +1832,27 @@ function menu_rebuild() {
 /**
  * Collect, alter and store the menu definitions.
  */
-function menu_router_build() {
-  // We need to manually call each module so that we can know which module
-  // a given item came from.
-  $callbacks = array();
-  foreach (module_implements('menu') as $module) {
-    $router_items = call_user_func($module .'_menu');
-    if (isset($router_items) && is_array($router_items)) {
-      foreach (array_keys($router_items) as $path) {
-        $router_items[$path]['module'] = $module;
-      }
-      $callbacks = array_merge($callbacks, $router_items);
-    }
-  }
-  // Alter the menu as defined in modules, keys are like user/%user.
-  drupal_alter('menu', $callbacks);
-  $menu = _menu_router_build($callbacks);
-  _menu_router_store($menu);
+function menu_router_build($reset = FALSE) {
+  static $menu;
 
+  if (!isset($menu) || $reset) {
+    // We need to manually call each module so that we can know which module
+    // a given item came from.
+    $callbacks = array();
+    foreach (module_implements('menu') as $module) {
+      $router_items = call_user_func($module .'_menu');
+      if (isset($router_items) && is_array($router_items)) {
+        foreach (array_keys($router_items) as $path) {
+          $router_items[$path]['module'] = $module;
+        }
+        $callbacks = array_merge($callbacks, $router_items);
+      }
+    }
+    // Alter the menu as defined in modules, keys are like user/%user.
+    drupal_alter('menu', $callbacks);
+    $menu = _menu_router_build($callbacks);
+    _menu_router_store($menu);
+  }
   return $menu;
 }