I subscribe to my wife's iCal calendar. It now appears 20 times in the list of subscribed calendars - each one apparently syncing. It crashes iCal every time.
Remove the following to the trash and restart your computer:
Home > Library > Caches
Home > Library > Calendars > Calendar Cache, Cache, Cache 1, 2, 3, etc. (Do not remove Sync Cache or Theme Cache)
If that does not resolve the issue,
Remove the following to the trash and restart your computer:
Home > Library > Preferences > com.apple.ical (There may be more than one of these. Remove them all.)
__You may have to re-subscribe to your wife's calendar after you restart the computer.
Do all the steps I indicate together.
Remove the following to the trash and restart your computer:
Home > Library > Caches
Home > Library > Calendars > Calendar Cache, Cache, Cache 1, 2, 3, etc. (Do not remove Sync Cache or Theme Cache)
Home > Library > Preferences > com.apple.ical
If that does not resolve the issue Safe Boot your computer by restarting and holding down the "shift" key until you see the Apple with a spinning gear. Eventually you will see the word "Safe Boot" across the screen in red.
Once the system boots up, go into iCal and delete the subscribed calendar(s).
Remove the following to the trash yet again and restart your computer normally:
Home > Library > Caches
Home > Library > Calendars > Calendar Cache, Cache, Cache 1, 2, 3, etc. (Do not remove Sync Cache or Theme Cache)
Home > Library > Preferences > com.apple.ical
This problem is often caused by a little piece of software that is installed to make Zimbra work. It is called Zimbra connector, in System Preferences.
On an updated mac, that will cause ical to continuously make copies of the calendar.
The solution is very, very easy. Remove Zimbra connector from System Preferences (right click, remove), remove and re-add the Zimbra account in iCal and everything should work. (make a backup before you do this and make sure to write down your account details!)