When I delete all tasks from previous dates (which remain active until I do) all disappear except one which remains as a 'ghost' image & will not be deleted or removed. How do I get rid of it?
I suspect that it's just a typical Microsoft bug.
If you delete lots of items, it gets confused about what your deleting (for example, sometimes when you right-click an item, it offers to let you delete all from an entirely different date - one that you've already removed.) It seems that a bug means that you can never delete the final item.