Conflict with Classifieds plug in - please help

Hi, I have installed the Classifieds plug in and it seems to conflict with my site.
I am using GeoTheme and with the plug in installed/active it stops posts to the site....at least part of the site.
So here is the site - http://localbug.co.uk/

When someone puts a listing on it shows fine here - http://awesomescreenshot.com/0762h1lh5e

But then when you click to view the business listing it goes to a 404 error here - http://awesomescreenshot.com/0be2h1m59c

Obviously this is showing it as it should be and not with the error.

Can you please help as i really want to incorporate a Classifieds section.