Im having some what the same problem, I just loaded a fresh copy of zen and works great, except when I try to load the layout boxes page i get an error :

Warning: Unexpected character in input: ''' (ASCII=39) state=1 in /home/a6928564/public_html/admin/includes/languages/english/layout_controller.php on line 47

I tried to simply replace the existing page but it didnt not help, i installed a template clean business and cant access to enable side modules. but the problem was happening before i installed the template.

any clues, besides starting with a fresh install again? my server limits me on how much i upload in 24 hrs, but i need get backup and running