Individual Course pages not showing

Individual course pages are showing errors when pages are clicked to from this page: http://www.markhallam.net/cadman/training-in-word-endnote/

(Just click buttons to see what I mean!)

The first page shows the wrong url and the error 'this page has a redirect loop'. The two other pages show a 404 error. Perhaps this is because I changed the course url and then changed it back again? Could it have created an error in the .htaccess file?

An example original course address was: http://www.markhallam.net/cadman/training-in-word-endnote/professional-shooting-editing-video-on-the-iphone/

instead it is sending the visitor to: http://www.markhallam.net/cadman/store/products/technical-writing-training-course/

I have allowed wpmudev admins to acess the site. This is really driving me out of my mind and I have a client waiting.