Classified - edit ad link broken

Hi

I've installed the Classified plugin on my website.
I can add new ads. When I click on the link to edit an ad, it can't find the page.

The generated link is something like this:
http://innovationdistricts.org/edit-classified/?post_id=699

My permalink setup is: /%category%/%postname%/

Every once in a while, the link generated is
http://innovationdistricts.org/opportunity/profiles/maraleen/listings/create-new/?post_id=699
which is correct and loads the edit form.

Why does the code generate an incorrect link most of the time for the edit button?

Regards