Portfolio grid photos lead to 404 page

I have another issue with the site http://www.caninecontrolcompany.com. WP and Theme are up to date (new release of theme today, but I don't wish to install it until this problem is solved).

I am using the "day and name" permalinks structure, though I inherited the site with the default /?P=123 style of URL.

When I visit the gallery photo grid and click on a photo, I go to the 404 page. So far as I can tell, the permalink URLs look fine. I've attached some screen shots.

Here is some additional information. This is a "onepage" theme. To get a page to appear in the onepage and also be accessible as a discrete page via menu link, it was necessary to create an additional menu item as a link, with the url of the page in it. When I set up the URL as a "day and name" style, like caninecontrolcompany/solutions/ I would get a 404 error. When I set it to the default url "caninecontrolcompany/?page_id=122 it works fine.

What am I missing here?

Thanks for your help.

Stu