How can I fix iCal that is jammed/frozen/nonresponsive after trying to past in a calendar entry. I've restarted program and computer. Unable to remove entry and associated message "the server responded with an error" ICal stuck updating. Help?

I was trying to past an entry and the iCal program froze with an error message that can't be deleted, the program stuck indicating updating and totally non-reponsive. i can only exit by force quit. It is stuck on yesterday which is the day I was trying to paste an entry. I think the entry was too large. How can I get out of this. i've restarted the program and the ocmputer but it doesn't change. I wonder if I could use time machine to go back to a previous cal version? Any ideas? I have my cal also on iphone and at icloud so I am not at a total loss. Except that i cal is now totally non functional.