Authorize.net plugin not requesting payment details on shipping-only products

[narwold]

I'm using Authorize.net as my payment service. I have several free products, but we charge shipping for them. Whenever I try to purchase these free products, the shopping cart shows a positive balance for the total cost because of the shipping charge. However, the payment module doesn't seem to pick up on the shipping cost, and it refuses to ask for credit card details. The button on the checkout page says "Confirm Purchase", and it goes straight to confirmation if I click it - no requesting of credit card details. What can I do to resolve this?

[jenkinhill]

Try setting the product price as 0.001

[narwold]

I thought that might be a solution, but for some strange reason that doesn't seem to make a difference.