Hi David,
Please check the following:
1. In the DNN module settings of the Xmod module on your listing page - Do you have registered users can edit module checked?

Registered users should not have edit rights on this setting. Xmod handles the security setting internally based on the security settings tab on the Configure Xmod Module page.

By default Administrators and the Host account can view and edit all records.
The user that is assigned to the listing should only be allowed to edit their own listings.
While logged in as Administrator, also check who was assigned the listing in the Admin panel portion of the form. You can log in as that user to test if you have your security settings correct.
FYI - next week I will be creating another training video that will show you how you can set up a Your Account page by creating a new DNN page, adding a XMod instance to that page and configuring the XMod module so a user can only view and edit their own listing(s).
Business Directory Video Training
Buck |