If you change a recurring event on a Palm, it may be moved to the Unfiled calendar in iCal when you sync the Palm with iSync.
Symptom
When a recurring event is modified on a Palm OS-based device and then synced with iSync, the event is moved to iCal's Unfiled calendar. This potentially creates a duplicate in the Unfiled calendar of an event that is already in another calendar ("Home", for example).
Solution
If the event was originally in the Unfiled calendar in iCal, it will not be moved to another calendar type.