Index: wp-admin/js/nav-menu.js
===================================================================
--- wp-admin/js/nav-menu.js	(revision 25376)
+++ wp-admin/js/nav-menu.js	(working copy)
@@ -178,6 +178,11 @@
 							var t = $(this),
 								listItemDBIDMatch = re.exec( t.attr('name') ),
 								listItemDBID = 'undefined' == typeof listItemDBIDMatch[1] ? 0 : parseInt(listItemDBIDMatch[1], 10);
+							
+							// Only show top level items
+							if (0 !== t.closest('ul.children').length)
+								return;
+							
 							if ( this.className && -1 != this.className.indexOf('add-to-top') )
 								processMethod = api.addMenuItemToTop;
 							menuItems[listItemDBID] = t.closest('li').getItemData( 'add-menu-item', listItemDBID );