Add to Cart from Manufacturer Search not working

[chill_e_g]

VM 2.0.26d
Joomla 2.5.19.

I may need someone to physically check this problem. www.shop.scrapbookstudio.co.za

I have added an add to cart in category view, it works fine, modal box pops up and item gets added to cart.

When I view products by manufacturer the add to cart button takes me to an empty cart : http://shop.scrapbookstudio.co.za/custom-filters-results/no-category/3-bugs-in-a-rug

Hope someone can assist, as I do not have enough knowlegde on how to debug this. Let me know if you need any access details