I think I figured out what happened:

•A non-refundable $75 fee (per passenger) is applied for award bookings made less than 21 days from the travel date. Dividend Miles members with Gold, Platinum or Chairman's status are exempt from the quick ticketing fee.

Initially the last segment of my flight was displayed on the website as October 2013 instead of October 2014 so the system may have thought it was less than 21 days. Then it realized October 2013 was last month so it was cancelled and then later corrected.