Wow, thanks for the fast response! It sounds like this will be taken care of in the next update, so that will be fine. What file should I look in though if I want to try and fix this myself before then?
I am also getting the same error on this. What I believe is causing this is that I have a free sample that does charge $1.99 for shipping. Paypal does not seem to like this. This is using PayPal Website Payments Pro (DoDirectPayment). It works fine on other quantities of the item that do charge, but the free one gives the 10413 error. I changed the price to a penny and it worked fine so it must be the free part. Any idea on how to fix this?