Hi,
The issue is either that you selected an invalid country in the "country" field of the warehouse area of the UPS shipping method settings, or that you selected an invalid country in the country of the user address during the checkout (or both).
Which country did you choose in both ? What are the settings of these if you edit them via the menu System>Zones ?
What if you select another country ?
I couldn't find much information about that error online. Has the UPS technical support any information to provide about that error message that you could tell us ?