I had already installed the suggested NET updates. Everything now seems to be working (for now):

"Hello SDL Support,

Thanks for getting back to me (eventually).

The problem was in fact the other way around, as everything was working fine until I installed the suggested updates.

I was fortunately able to continue work on a laptop, which I wisely did not update.

After much downloading, rebooting and sundry fiddling around, for which I really do not have time, everything now seems to be working fine on both computers.

It would be nice if downloaded updates (this is not the first time such things have happened) were not such a touch-and-go affair, resulting in some vital piece of kit going wrong for the duration.

Best regards,

Andy Birch"