You having asked that question has now raised doubt in my mind.
Most applications such as photoshop, lightroom , word all work ok.
Internet browsing is normal.
BUT, over the past few weeks, the TV card has stopped working (software has been reinstalled) and my daily scheduled data backup is not happening because the programme reports that the external drive is full, which it certainly is not.
I guess this points to a corrupted operating system.
I have a mirror image of the partitioned drive that contains the operating system and programmes which was done at the end of January. Little has changed since then.
So I guess I will restore back to then and see if this resolves the problem.