May anybody out there help to get LR working again.
Opening LR 5 I see message 'Lightroom encountered an error when reading its preview cache and needs to quit'. I have deleted the Preview Cache folder entirely (backed up). This does not solve the problem. What can I next do to load Lightroom?
If you have deleted the preview cache folder and the problem remains, then most likely you have found the wrong preview cache (it's the previews for a different catalog) and you need to find the proper preview cache. You should use your operating system's search feature to find all folders whose name ends with Previews.LRDATA, and delete each of them until you can open your Lightroom catalog.