Symptoms: Hosted calendars not showing up in iCal. Inability to add any calendars from server and inability for others to subscribe to a delegated calendar.
Causes: Breakdown of communication process between server and client while updating. Usually accompanied by “spinning beach ball” in iCal.
Fix: On the server: in Workgroup Manager find the affected user account and select the “Inspector” tab. Find the “ServicesLocator” entry and remove any “(null):(null):calendar” entries. On the client: move all .caldav and .calendar folders inside ~/Library/Calendars into a new directory. Delete the “Calendar Cache” file found in ~/Library/Calendars. Log out and back in. Restart iCal and re-add the login user’s account in iCal’s preferences. You may also have to add the old calendars back in.