Security violation on adding to cart

Hello, I'm setting up a Joomla/Gallery mechanism as a learning exercise.

I have a website that was developed for me with these tools and I'm trying to ensure that I can understand it and continue maintaining it myself rather than keep bugging my developer (who is also a friend). So I've got a testbed site and am playing. Best way to learn!

The gallery is set up and appears to work ok. http://www.studywright.com/gallery/main.php if I select one of the two items I can add it to a cart, just fine.

On the Joomla side I have embedded Gallery within it thus using the Joomla/Gallery2 bridge: http://www.studywright.com/index.php?option=com_gallery2&Itemid=26

Again it appears to work. However if I go to add an item to the cart it fails. I get a screen up saying "Security Violation. The action you attempted is not permitted."

I was actually doing this so I could investigate having pricing of different values in different albums but as I can't get beyond adding to an album I am a little stuck.

Can anyone suggest what I should be checking? The settings are (best I can see) the same between my working site and my test-bed.