Index: wp-admin/menu-header.php
===================================================================
--- wp-admin/menu-header.php	(revision 22098)
+++ wp-admin/menu-header.php	(working copy)
@@ -150,7 +150,8 @@
 
 				$title = wptexturize($sub_item[0]);
 
-				if ( ! empty( $menu_hook ) || ( ('index.php' != $sub_item[2]) && file_exists( WP_PLUGIN_DIR . "/$sub_file" ) ) ) {
+				// If the file doesn't exist in the admin directory
+				if ( ! empty( $menu_hook ) || ( ('index.php' != $sub_item[2]) && file_exists( WP_PLUGIN_DIR . "/$sub_file" ) && !file_exists( ABSPATH . "/wp-admin/$sub_file" ) ) ) {
 					// If admin.php is the current page or if the parent exists as a file in the plugins or admin dir
 					if ( (!$admin_is_parent && file_exists(WP_PLUGIN_DIR . "/$menu_file") && !is_dir(WP_PLUGIN_DIR . "/{$item[2]}")) || file_exists($menu_file) )
 						$sub_item_url = add_query_arg( array('page' => $sub_item[2]), $item[2] );