Try creating a new catalog and add a few images to it and let us know if the problem still persists.
Sorry - I accidentally activated a correct answer - I do NOT have a correct answer - my fault!
Appreciate your reply!
I sam unable to create a new catalog since the dialog box won't stay for me to complete the action.
This an other Lightroom issues never seen by me until my latest update are now appearing.
I am in communication with Adobe phone support.
Adobe phone support installed an earlier version of LR. No significant issues so far. I can do everything I used to do before the new version of LR was installed, still using the same catalog that the new version was using producing faults enough to make work impracticable. (All versions old and new were using a networked NAS for the DNG file storage and no operating systems or anything else has been changed.)
I will give a bit more info in a week or so's time - I should have time to do this then.