[Owncloud] Calendar shows loading forever?

[peter at chubb.wattle.id.au]

Hi folks,
   With 4.5.1, visitin the Calendar web-app, the spinning wheel spins
   forever in google-chrome, mozilla and safari.  And no events are
   shown.

   I can see the calendar in my caldav client.

   If I switch to a different app, the calendar events appear briefly,
   then vanish when the other app takes over the screen.

   Help?

Peter C