Found out what the problem was. Flight was not being displayed by AC (it only had a few seats left the day before when I looked at the seatmap, so I thought it was entirely sold out for some odd reason) as they had cancelled it.

However, codeshare partner JK (spanair) still had the flight listed but wouldn't provide seatmaps which was why I got a little confused. In fact, two weeks after AC went from 7x/weekly to 5x/weekly, JK is still selling the flight despite the fact that it doesn't exist! No wonder Star needs a common IT system!

Anyway, solved the problem by calling AC up - I had been rebooked on the day before (JAN 1st... ACK... Don't want to fly on New Years thanks), so I had them switch it to the 3rd which was the original return date that I wanted anyway (but not available for fare catagory). Also snagged 13A which IIRC is listed as a status seat but no other windows were available so agent had no problem with that.

So all in all a win-win situation, although it would have been nice if AC had called to tell me that they rebooked.

c.