I took the reboot option first: It would not destroy all my destination information and that seemed like the best way to go first. Disconnected the battery, waited about 15 minutes and reconnected. Then I drove around for awhile with a destination set. All seems to work perfectly now -- the red arrow/triangle stays right where I am on the map and does not get over to side streets several blocks away from my actual location, as it had been doing. Should it fail again, I'll go the the Master Resent option.
Thanks for both of you for your assistance.
Bill