Since I started this thread, I will add, for the record:
I had only one XP machine on my network.
With the arrival of Endpoint Protection 8.0.1606, when I moved the XP machine into my SOA group that gets program updates, the update was installed automatically and the problem stopped happening on that machine.
I did not have to update the SOA to get this result. I'm still running SOA 1.3.3.35 on a Win 7 Ultimate machine.
I am satisfied that this particular problem, as I reported it, is fixed.
Thanks to avast! staff.