Thanks for that, I am indeed running Windows 7 and at your suggestion downloaded "Windows6.1-KB3138612-x64".
It is described as the "Windows Update Standalone Installer".
When run it displays a MsgBox showing an endlessly running progress bar titled "Searching for updates on this computer".
Sadly, it still gets nowhere
98% System Idle Process. I have run Anti-Virus, MalwareBytes and SuperAntiSpyware with no reported problems. I have also used CCleaner.
Three further factors that seem "odd" are that:
1. the system seems to take a very long time to shutdown.
2. when booted it says:
"Preparing to configure Windows
Do not turn off your computer."
before reporting:
"Failure configuring Windows updates.
Reverting changes,
Do not turn off your computer."
3. it than says "
Microsoft Mouse & Keyboard Centre has stopped working."
I take it from the first two items that there are files previously downloaded that do not work.
Do you have any idea where these might be located (e.g. under C:\Windows\SoftwareDistribution\Download\)?
Would it be an idea to delete these?