The Hilton website had an announcement up during Sandy saying that cancellation fees would be waived for storm-affected areas. As mentioned previously, prepaid 'reservations' are really prepaid bookings that can't be cancelled. I know I canceled a reservation at a Homewood Suites with < 24 hr notice during Sandy, and was not charged. Since the Hilton site had the announcement, perhaps if the local property is not cooperating, try contacting Hilton customer support rather than the hotel.