I exited and reset (oh how I wish that didn't require taking off the cover, a feat I rarely manage successfully!) and that appeared to solve the problem.
I'm an end user, not a developer, but would appreciate someone explaining what might have happened here please. Does it sound like a bug with apMemo which I need to report to the author?
P.S. On trying to post this I'm getting a message saying I'm not logged in, yet I am! (At the top of this window I see 'Logged in as terrypin' I'll try again ...
Terry, East Grinstead, UK