Just after positing my question above, I stumbled on the following forum discussion on the same topic. The "Best Answer" offered a description of the cause, as well as a solution that worked for me. For anyone else having this problem, I suggest giving this a try.
Best Answer mcihelka , 22 October 2013 - 09:25
I am pleased to offer a definitive answer on this issue.
This issue comes about because Windows Update is heavily reliant on components of Internet Explorer. If these components are not up-to-date, later versions of Windows Update Agent (that's the engine that scans for and manages updates) may fail or exhibit very poor performance.
For folks that are doing a fresh install of Windows XP, the problem will always reveal itself when you try to do your first Windows Update. By initiating an update via the Windows Update website or enabling automatic updates, Windows will first upgrade Windows Update Agent. You cannot prevent this from happening. After that, Windows Update will fail or perform poorly thanks to the dated components of Internet Explorer 6.
For folks that have an existing Windows XP installation, this problem may still pop up if you have not been regularly updating your Internet Explorer installation.
It is NOT necessary to install a new version of Internet Explorer to resolve this issue. What is actually required is to install the latest cumulative security update for whatever version of Internet Explorer you have installed. This will be IE6, IE7, or IE8 (if you're doing a fresh install of Windows XP it will naturally be IE6). This will upgrade the various components of your Internet Explorer installation. Thereafter Windows Update will perform as it should.
The latest updates are dated October 2013 (as of writing this). Download and install the update that corresponds with your currently installed version of Internet Explorer:
For more information (or for details of updates suitable for 64-bit versions of Windows XP) see http://technet.micro...lletin/ms13-080.
Edited by mitchsc, 26 October 2013 - 04:06 PM.