Hi send a copy of the cart/checkout page. Im assuming that the shipping cost is automatic as in it doesnt require user interaction with chosing a specifc delivery option. Im assuming you are skipping the checkout page as you have the paypal button on the cart page which directs straight to the paypal site. I would do a test using my paypal account but didnt want to be charged in case it processes automatically without user intervention on the confirm page :)
Chris