I’ve had a similar problem. I wasn’t able to make any changes in many of the admin pages after the update.

I tracked the problem down to jQuery – as of jQuery version 1.9 many APIs have been changed or removed so an error was being thrown which stopped all javascript processing on a page.

As a temporary fix, I changed lines 35 to 37 in functions.php of therestaurant folder:

wp_deregister_script(‘jquery’);
wp_register_script(‘jquery’, ‘http://ajax.googleapis.com/ajax/libs/jquery/1.4.2/jquery.min.js’);
// wp_enqueue_script(‘jquery’);

This allowed me to use the wordpress backend again, but what features have I lost now?

Hopefully that’ll help your dev team track down the issue.