To fix the JTableMenu::_getNode Failed - Error building Admin Menus problem run the following query in your MySQL administrator tool:

INSERT INTO `MyJoomlaDatabase`.`prefix_menu` (`id` ,`menutype` ,`title` ,`alias` ,`note` ,`path` ,`link` ,`type` ,`published` ,`parent_id` ,`level` ,`component_id` ,`ordering` ,`checked_out` ,`checked_out_time` ,`browserNav` ,`access` ,`img` ,`template_style_id` ,`params` ,`lft` ,`rgt` ,`home` ,`language` ,`client_id` ) VALUES ( '1', '', 'Menu_Item_Root', 'root', '', '', '', '', '1', '0', '0', '0', '0', '0', '0000-00-00 00:00:00', '0', '0', '', '0', '', '0', '427', '0', '*', '0');