1. Connect your BB via USB to your PC, and Open Desktop Manager on your PC.
2. Open up Backup/Restore > Advanced.
3. From Advanced you'll see a split pane screen. You won't see anything in the left pane. In the right pane will be the databases currently on your handheld device.
4. Highlight on the right side your Address Book database (OR your Calendar database) and click the CLEAR button at the bottom of that screen.
5. After it's finished, close the Backup/Restore window, and check the device to make sure the address book (or calendar) has properly cleared out.
I followed those instructions and the data still remains on my BB. But now when I open the Backup/Restore window, the Calendar entry under Device Databases has nothing in the entry column.
Also, when I try to delete the calendar entries on my BB, I get this message:
"Appointment Deleted externally. Changes will be lost and the viewer closed."
So I click on "ok" and nothing happens.