Upgrading WP: Core, themes and plugins.

wordpress/wp-admin/network/plugin-editor.php

@@ -8,9 +8,9 @@
  */
 
 /** Load WordPress Administration Bootstrap */
-require_once( './admin.php' );
+require_once( dirname( __FILE__ ) . '/admin.php' );
 
 if ( ! is_multisite() )
 	wp_die( __( 'Multisite support is not enabled.' ) );
 
-require( '../plugin-editor.php' );
+require( ABSPATH . 'wp-admin/plugin-editor.php' );