subpage menu not following menu structure

I can’t find anything on this…

My site is http://www.bengoode.com. Take a look at the homepage top level navigation structure, and then navigate to a subpage – note the difference.

The subpages are displaying a different nav structure to the homepage. Any ideas?

This only happened two days ago, when I added a new subpage.

I have tried the following:
Delete the menu, and create again
Create other menus with the editor
Ensure my .htaccess file is writable
Remove page ‘order’ for all subpages
Pasting in a static nav in the header.php file – this still didn’t work which really puzzles me!

Another thing I’ve noticed is the new WP admin header only appears on the homepage, not sure if it should also on the other pages – could suggest something wrong with my page file?