Our store needs to have a flat rate of $5.99 for shipping. In the Smith Cart manual it describes that I can do this by setting the shipping to Free Shipping, entering in my ammount ($5.99) in the handling field, and checking the "Combine Shipping and Handling" checkbox.

However, when I do that I then start getting the message "A critical error has occurred" when I click add to cart for any product, though it does appear to add the product to the cart. When I click checkout, it just returns me to the store front page with the critical error message.

Any idea what I'm doing wrong here?

-Andrew