OK, did that, but I'm still getting the same error.

Do I have to configure a Shipping Zone for this module to work? My settings are these:

Enable USPS Shipping: True
Enter the USPS Web Tools User ID: *********
Which server to use: production
Handling Fee: 0
Tax Class: --none--
Tax Basis: Shipping
Shipping Zone: --none--
Sort Order: 3
All Packages are Machinable: False
USPS Options: Display weight, Display transit time
Domestic Shipping Methods:
EXPRESS, PRIORITY, FIRST CLASS, PARCEL, MEDIA, BPM, LIBRARY
International Shipping Methods:
Express Mail Int, Priority Mail International, Priority Mail Int Flat Rate Box, First Class Mail Int Package, First Class Mail Int Parcels
Debug Mode: Email

I do have a shipping zone set up for the United States, but nothing explicitly created for International. (And not totally sure how I'd go about creating that.)

Thanks,
Tim