The system indicates that new listings can't be added because there are no established categories... nevertheless, there is a category field in the form, associated with post category, and it has three available options.
I have searched on the web, and found that other people have faced the same problem... so I had to uninstall this plugin, and I am still looking for another one...
It is said that it doesn't work, because this plugin seemed so promising and powerful...
http://wordpress.org/extend/plugins/business-directory-plugin/