Kmail 5.10.0: Empty message-list pane & message-body pane

Trying out Kmail 5.10.0 under plasmashell 5.14.4 I've come across a very 
unexpected problem.

Kmail starts normally amd has clearly picked up the maildir DB in ~/mail
(the folder list is correct and each folder shows the number of 
messages in the folder.)   Addressbook & filters are there.

BUT, both the message-list & message-body panes are EMPTY!
   (Headers: Subject/From/Date)
   
No evidence that any indexing is going on, even after leaving it running 
all 
evening.

'New message' goes through the motions of working but nothing sent 
arrives 
anywhere. 

   Baffled. :-(

Help!

-- 
/\/\aurice