Index: wp-includes/l10n.php
===================================================================
--- wp-includes/l10n.php	(revision 19770)
+++ wp-includes/l10n.php	(working copy)
@@ -382,9 +382,17 @@
 
 	load_textdomain( 'default', WP_LANG_DIR . "/$locale.mo" );
 
-	if ( is_multisite() || ( defined( 'WP_INSTALLING_NETWORK' ) && WP_INSTALLING_NETWORK ) ) {
+	if ( ( is_multisite() || ( defined( 'WP_INSTALLING_NETWORK' ) && WP_INSTALLING_NETWORK ) ) && ! file_exists(  WP_LANG_DIR . "/admin-$locale.mo" ) ) {
 		load_textdomain( 'default', WP_LANG_DIR . "/ms-$locale.mo" );
+		return;
 	}
+
+	if ( is_admin()  )
+		load_textdomain( 'default', WP_LANG_DIR . "/admin-$locale.mo" );
+
+	if ( is_network_admin() || ( defined( 'WP_INSTALLING_NETWORK' ) && WP_INSTALLING_NETWORK ) )
+		load_textdomain( 'default', WP_LANG_DIR . "/admin-network-$locale.mo" );
+
 }
 
 /**
Index: wp-admin/includes/admin.php
===================================================================
--- wp-admin/includes/admin.php	(revision 19770)
+++ wp-admin/includes/admin.php	(working copy)
@@ -6,6 +6,13 @@
  * @subpackage Administration
  */
 
+if ( ! defined('WP_ADMIN') ) {
+	// This file is being included from a file other than wp-admin/admin.php, so
+	// some setup was skipped. Make sure the admin message catalog is loaded since
+	// load_default_textdomain() will not have done so in this context.
+	load_textdomain( 'default', WP_LANG_DIR . '/admin-' . get_locale() . '.mo' );
+}
+
 /** WordPress Bookmark Administration API */
 require_once(ABSPATH . 'wp-admin/includes/bookmark.php');