Nevin Pratt wrote:

> As far as I can tell, that doesn't tell me anything about why the 
> Microsoft IIS server at "testing.shippingapis.com" is treating the two 
> requests differently-- why it works fine when my browser is the client, 
> but returns a "400 Bad Request" error when Squeak is the client.

You will need to look at what the browsers are sending.
One way would be to open a listening socket in squeak on port 80 and 
then connect to it with your browser with a url like
http://localhost/ShippingAPITest.dll?API=Verify&XML=<AddressVa ...etc

Or even before that look at how squeak actually parses the URL.

Michael