I have some products with add options and some with just add to cart. The add options button works fine, but when you click add to cart, I get an error saying A critical error has occurred. Object cannot be cast from DBNull to other types. I found this thread http://www.smith-consulting.com/Forum... and saw that it is related to when I have category discounts enabled. If I disabled them, then the issue goes away. We are running smith 4.52.0 on dnn 06.00.02 . Is this fixed in your most recent version of the software?