05-11-2010 09:36 AM
I had the same problem when trying to just sync a portion of my calendar (I think it was 30 days in the past and 180 days in the future) but it wanted to change 85% of my calendar. I canceled out of the sync, backed up my calendar and then resynced. Sure enough, it deleted the majority of my calendar.
I just went in and imported my calendars from the backup I had just done and synced all calendars.