Multiple Image Windows in Shop

Hi
I have recently installed WooCommerce on my site and been adding a few images to the shop. They all appear fine, however when I select am image it gets opened in the Product Description window, however it I then select it again it opens the image up big, however I have to close 2 windows to go back to the original page.

Anyone any ideas why this happens?

Check this link and click on the main image to see what I’m talking about.

http://landscape.martinspencephotography.co.uk/shop/fishermen-at-woodburn-reservoir

Thanks
M