Can't Delete Events or Calendars

Question

Hello,
I have a very modest iCal setup, 3 calendars, syncs only to my personal iPhone, no MobileMe backup.
Today I copied an event to the clipboard and pasted it in somewhere else. That led quickly to a situation where new events and calendars could be created but not deleted. Deleting or moving an event or calendar causes it to reappear immediately. My calendar is now corrupt and full of garbage I can't get rid of.
In order of preference, can someone tell me how to:
1) Stop this happening
2) Restore from iPhone, overwriting the iCal data on the computer
3) Wipe the current iCal calendar entirely so I can start from scratch, as if I had never used iCal before
Option 3 would involve probably less than 5 minutes of work repopulating the new calendar, so if the other two options are difficult or involved, it would be preferable.
Thanks in advance for any help.

Answer 1

The problem is solved.
The command that solved the problem was:
*sudo chmod -a# 0 ~/Library/Preferences/*
The brief shell script that diagnosed the problem was:
#!/bin/sh
*ls -l@ed /*
*ls -l@ed /Library/*
*ls -l@ed /Library/Preferences/*
echo
*ls -l@ed ~/*
*ls -l@ed ~/Library/*
*ls -l@ed ~/Library/Preferences/*
*exit 0*
The problem arose when a calendar event was copied to the clipboard, then pasted back to a different day, during an iTunes 7.1 software update.