I mentioned the 31st since that's what Tokyoite found.
I've read about people having the issue with prices jumping to segment-by-segment pricing before.
But since booking by phone seems to be the way out I wouldn't call this "sort of" being able to book.
Coming back to your issue, it is important that the itinerary can be found as a single connecting flight and not 2 separate flights.
I mentioned this in another thread already, Aegean will only ticket awards that are in Starnet (?) as a single connecting itinerary and will not piece together individual flights.
Obviously, this has nothing to do with the pricing issue though.