Thanks for posting back with the info. It looks like there are two things going on, with the Express Checkout process call you are getting this error in return:
Express Checkout PayerID is missing.
The PayerID value is invalid.
With the UPS call you are getting this error:
The requested service is unavailable between the selected locations.
I think that both of these are related since the request for the UPS does not contain any of the ship to details. It looks like it is a result of the PayerID not being present. I'm opening a ticket for you on this issue so it can be looked into further. To check the status or update the ticket login and visit your support history.