security_patch stopped the add to cart from working on one of my sites

[cjsmiff]

Hi,

I have just applied all security patches to my site but had to remove security_patch_v138_20080919.php because it stops me from being able to add any items to the cart on the website. I get sent to the 'your shopping cart is empty' page.

I don't have this problem on any other sites that I have applied this patch to.

I'm using 1.3.8a running on PHP Version: 5.2.12 (Zend: 2.2.0) and Database: MySQL 5.0.89-community.

I have checkbox-style attributes assigned to the products but according to this http://www.zen-cart.com/forum/showthread.php?t=108428 this patch should work.

Any suggestions please?
http://www.rugscentre.co.uk

Thanks
Claire