Index: wp-includes/query.php
===================================================================
--- wp-includes/query.php	(revision 20831)
+++ wp-includes/query.php	(working copy)
@@ -2343,6 +2343,7 @@ class WP_Query {
 
 				switch ( $orderby ) {
 					case 'menu_order':
+						$orderby = "$wpdb->posts.menu_order";
 						break;
 					case 'ID':
 						$orderby = "$wpdb->posts.ID";