I received a final answer from lm_sensors support--they found that the
voltage limits in the via686a section of the default configuration file were
wrong for my setup. They sent new ones to plug in (quite a few more than
were in the default file!) and once I did that, ran sensors -s, then ran sensors,
everything was fine.
Once they started work on my ticket, they answered my subsequent
reports on trying what they suggested almost as fast as I could send
my own emails. Very impressive and helpful user support!