"No shipping options available" for one country

I have added numerous countries into an "International" category of GeoZones. One of those countries, Serbia, isn't working. I'm getting an error "Warning: No Shipping options are available. Please contact us for assistance!" when selecting that country in my shopping cart.

I am using "United States Postal Service" shipping module, and "All Zones" are selected.

All other countries in the International GeoZones seem to be working.

Any suggestions?

Alex

Are you sure that USPS ships to Serbia? I haven't ever tested it, but check that it works on USPS's site. If not, that could be the reason.