MacLars,
Welcome to Apple Discussions.
Before you do anything use iCal>File>Export...>iCal Archive... to save a copy of your data to the Desktop.
Then:
1. Use iCal>File>Export...>Export... for "Calendar," and save the "Calendar.ics" file on the Desktop.
2. Delete "Calendar" from the iCal sources pane using iCal>Edit>Delete. Quit/Restart iCal.
3. Add "Calendar.ics" by using iCal>File>Import...>Import..and click on "Calendar.ics." Click on "Import."
4. The "Add events" window will appear.
5. Choose the "Home" calendar from the drop down menu in the "Add events" window.
If you are not satisfied with the results you can always use iCal>File>Import...>Import... on the iCal.icbu file which you created and saved to the Desktop.
;~)