Thanks Greg - and Josagan - for your suggestion. It does sound as if the update can be safely installed when all USB devices have been unplugged first.
I'm not willing to risk it though because individual configurations might have a bearing, and I've wasted a lot of time in October and in the last few days on the irresponsible update.
As unplugging USB devices prior to installation sounds so credible and logical, why aren't Microsoft testing the solution on some machines of their own?
When is Microsoft going to take full responsibility for the time and expense wasted by its customers with dangerous updates.
If Greg's and Josagan's solution is confirmed, why aren't Microsoft offering the update with bold instructions to unplug USB devices before installation? - That is, NOT allowing auto-updates for this software!!
Volunteer Susan Bradley should not be landed with problems inflicted by Microsoft, but I will email Susan so that she can open another case and hopefully provoke some responsibility without further delay!!! - Phil