issue with free products in marketpress using Paypal Express

I have a product that I want to give away but still charge shipping for. When I set the product for $0.00 price and no shipping, MarketPress will use the 'manual payment' gateway and will automatically process the order. When I setup a $1.50 shipping price for the product using Paypal Express Checkout, I get the following error during checkout:

There was a problem connecting to PayPal to setup your purchase. Please try again.
10413 - Transaction refused because of an invalid argument. See additional error messages for details. - The totals of the cart item amounts do not match order amounts.

Any ideas on how to setup a free product with shipping using Paypal Express?