Thanks Paul,
It worked!
Just for completeness: after making the changes you suggested, I also deleted all the .o files in the Ethernet directory to get them to recompile. I don't know if that was necessary, but figured it couldn't hurt.
There are still some strange behavior with the sketch apparently hanging for about 20 seconds after it gets the last byte from the server. I'll see if I can solve that issue myself. If not, I'll start another thread.
Thanks again for your help!
--
Ben