my theme breaks when I go to edit/add classified

Hi,
I have set this page up just to see what the shortcodes do.
http://www.everything-united.co.uk/aaa-test-page/
All pages come up fine but when I click on Add/Edit classified my theme breaks.
http://www.everything-united.co.uk/aaa-test-page/
It is using 'page.php' to show these items. This theme file seems to be ok for all the other pages but not for this one.
Not sure what I have done wrong here or where to go to fix it.
Any help would be appreciated.

Many thanks
Jo