Product image not expanding when clicked

Hello,

I have just launched my opencart site adn I have disovered that when you click on a product image in the product page, that it doesn't expand like it should (like lightbox). Instead of the new window starting small and expanding, it startts large and contracts down to a thin line in the middle of the screen.

My site is: www.fairdinkumfakesandoriginals.com.au

Can someone please help me with this.

Thanks,

Peter