When checking out with PayPal, it appears the Joomshopping is sending providing my state of residence as "California" which I selected at time of checkout. However, Paypal won't accept that as a valid shipping address. All addresses in the US must have the two letter state code, rather than the full written out state.
Is there a way to fix this? by the way I have installed a State Tax module from JoomShopping, which may be a factor here.