This just started happening a couple of days ago. I am connecting to my Google calendar via CalDAV. Normally I see my calendar listed under "Google" in the calendars pane on the left. I then have some delegates, that usually appear in the Delegates section in the same pane.
For some reason, what's happening now is that I still have the delegates, but the shared calendars are now appearing under the "Google" heading as well. So I get each calendar listed twice. Worse, I am getting alarms going off for events that shouldn't have them. I think this is because Calendar is applying a default alarm to what it thinks is a new calendar.
Any way around this? If I force quit CalendarAgent, it works correctly until it refreshes the calendars, and then it all goes haywire again.