This issue took quite a long time to resolve but kudos to Kaspersk's "help" gurus who kept trying.
They could not fix it but after they had worked on the computer remotely I ran updates of everything, which included a new update from Microsoft. For some reason this worked and Kaspersky came back online working as before.
The conclusion was that something in the Microsoft updates had clashed with Kaspersky.
I was certainly impressed by the help I received from kaspersky in this matter and would recommend this software to anyone.