ical problem...

For a few days now... I am getting this dialog box in iCal https://p02-caldav.icloud.com/1336181237/principal/ is not a location that supports this request.

Surely its something stupid I have done. So.. Anyone??? I am running 10.10.5 on a late 2009 macbook. Until a few days ago.. all was fine.

Thanks for your time!