Connecting Phone to PC...USB socket seems to be dirty
First, I powered off the phone.

Then, I took some contact cleaner (the kind used to clean old TV tuners and potentiometers) and sprayed it into the female USB port.  I plugged and unplugged the male USB plug several times.  I blew out the port with compressed air and powered the phone back on.

Success!

(thanks for the suggestions and comments)