Thanks for the suggestion.

Somehow (magically?) the contents now show, and can be edited! (I changed nothing.)

 I only posted on the forum the second time contents was not visible, several reboots after the first occurrence, Go figure!

For one of my several address books, I don't see any entries. I do for all others.

The address book is listed, and sending to a distribution list using names from it works, but I can see the entries in the Tech WG address book.

I can see the entries in all other address books.

Not being able to click on an addressee, I can;t edit his entry.

I suggest renaming the addressbook to a name without a space, perhaps to Tech_WG.  Restart Pmail.  If addressbook content is still not visible try reindexing it.