If you find the answer, please let me know. TIA.
In my case it turned out to be my fault. I had the wrong hostname in there.
It was a real host - you could ping it, but it was where the SMTP server
was located, not the POP server. (Doh!) My ISP has two different
systems for these purposes and I had the names backwards.
It works correctly now, though I do notice I must specify the hostname
on the fetchmail command line to prevent it from trying to connect
to another host in the .fetchmailrc file, even though that other host
is marked "skip" and the one I want is marked "poll".