what I’ve tried is to do this:

// ModelsInit.order.removeShippingAddress();
           // ModelsInit.order.removeShippingMethod();
                    ModelsInit.order.estimateShippingCost({
						zip: null
					,	country: null
					});

Take look at the OrderWizard.Module.Shipmethod that module. But when exactly is this error appearing when the user adds an item to the cart? or when it gets to the checkout section?