I have iCal set up attached to my Google Calendar, and thus events entered into iCal, Google Calendar or my iPhone all happily sync up. Except today new events entered into iCal stopped appearing in Google or iPhone.
Found a quick and easy solution.
1. Exit iCal
2. Find the file [youruser]/library/calendars/calendar cache and delete it
3. Restart iCal
And hey presto entries added to iCal are syncing again.