Spybot 1.6.2 Vista Home Premium SP1
As stated above, used ok on this vista machine since Sept 2007.
Update problem and freeze on interrupt developed in March or April 2009.
None of the fixes (replacing sdupdate.exe, admin privs, XP compatibility mode) fixed the problems.
HOW I FIXED IT:
I uninstalled Spybot.
I downloaded a fresh copy of version 1.6.2 and installed.
I now can update and interrupt scanning without problems.