OK so it is Monday Morning and I tried again to update the last of 10 sites with update manager. I uninstalled the update manager and reinstalled it. I went through the motions of updating. I got the messages, "unable to write entry", and "failed to extract archive" during step three. When I navigated away and back to try again I got no update found and the version in the corner was up to 1.5.18 (current version).
It appears all my sites are now up-to-date. Next version update will be the test.
My problem seems to have fixed itself.
Thanks,
Jeff