products not appearing in shopping cart

[ianpanorton]

Hi - I know there are other posts on this subject, but I can't find an answer I can understand.
I'm running Joomla 2.5.13 and VM 2.0.22a.
URL: http://www.pro-practice.tv
Nothing happens when I click on the add to cart button, but if I refresh the page, the product appears.
Cache is not turned on, and I'm using my Bamboo template's jQuery, not VM's.
Has anyone any ideas?
Thanks
Ian