jessie-kvm-qemu: Win7 guest fails to update

[Frank Miles <fpm@u.washington.edu>]

I have two jessie systems with kvm-qemu virtualized Windows7 guest OSs.
These are mostly working well (including guest inter-networking) to
the extent that I use Windows, with one glaring exception: when I try
to do a Windows Update - the process never finds anything to do, nor does
it ever terminate.  Ordinary Windows systems (belonging to other users)
are finding lots of updates and fairly quickly.

One of these is my home computer (Win7Pro); the other is my work computer
(Win7Enterprise).  Both were afflicted approx the same time (not sure exactly
when, I use the Win7 guests less than once/wk).

I've talked to our network/user-systems techs/admins, and they haven't a
clue.  They recommend their usual solution - full reinstall of Windows.
A hideous amount of time (ISTM) especially for my home system on a slow
internet feed.

Has anyone else seen this?  And better yet, found a solution?  DuckDuckGo
has not helped so far...

   TIA for any clues!