After:

1. setting Microsoft FAX to Manual using Control Panel, Administrative Tools, Services, Fax and changing Startup Type to Manual, then File, Exit;

2. removing the FAX icon from the Printers Window via Control Panel, Printers, and right-click on FAX icon, then delete, then close the Printers window

the problem has not occurred since.

I then installed Mighty-Fax from www.rkssoftware.com to supply FAX services, and which does not cause the same problem.