#2 SetExpressCheckout fails with when item quantity is defined

[Anonymous]

SetExpressCheckout request fails with error code 10413: "The totals of the cart item amounts do not match order amounts."

Problem seem to be in Payment class, getNVPRequest -method where ITEMAMT field is being calculated. Only problem with the calculation is that it disregards items L_QTY field thus making ITEMAMT field value inconsistent with summed payment items total amount.