Save failed with the following error: MenusTableMenu: :_getNode Failed –

This is problem from menu table on database of your site, you can fix it as follows

Seems that in your menu table, it’s already have menu with ID=1. So, if you can go directly to row with ID=1 to update value and make sure that it ‘s the same with: ( ‘1’,”,’Menu_Item_Root’, ‘root’,”,”,”,”,’1′,’0′, ‘0’, ‘0’, ‘0’, ‘0’,’0000-00-00 00:00:00′,’0′,’0′,”,’0′,”,’0′,’0′,’0′,’*’,’0′)

To solve this problem please do the following two steps.

1. Add the missing record to the database
Log in to phpmyadmin and execute the following statement
INSERT INTO `DATABASE_NAME`.`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’, ‘0’, ‘0’, ‘*’, ‘0’)

2. Rebuilding menus
Go to the administrator panel of joomla.
Menus –> MenuManager
Select all menus
Click on the button ‘Rebuild’
(By doing step two, the field ‘rgt’ in the just added record (step one) will get the appropriate value.)

I’ve tested this solution several times and each time with positive results.