I also have this issue with a very similar error code. I have had the wordpress reinstalled and the database reinstalled from a backup when the site worked properly.
The error code has gone now when I click on customise from the right panel wp menu.
I deactivated all the plugins and changed themes to a generic theme such as Twenty12.
I still have the same problem – I can not add a new menu and I can not add pages such as contact to the menu.