Rejected when authenticating to Sharepoint, but IWA works

I have a Sharepoint site that I can open just fine through IE, via integrated Windows authentication, but which I cannot open through Java.

This just prints "Feeding username and password for ntlm" 10 times and then quits.

If I use a browser that isn't configured for IWA, such as Opera, I get prompted for my credentials and I get right in, using the credentials just as they appear in the code.

So why do my credentials get rejected when I supply them programmatically?

I'm sure you've read these already but it might be worth looking at it again:

http://java.sun.com/javase/6/docs/technotes/guides/net/http-auth.html

and

http://spnego.sourceforge.net/pre_flight.html

Oh I read them all right. Understanding all of what I read is another matter.

As it happens, if I use the IP address it works fine. So my guess is that something between me and the dns is screwing it up. Like the load balancer doesn't like my using the application port, assuming everyone uses port 80, something like that. It would not surprise me overmuch: I'm more or less sure I'm the first person ever to try to read the Sharepoint data programmatically, as it's a pretty new environment.