After three days of trying to book on line and continuing to have the problem described in # 592, I connected with the CO tech support desk, and they talked me through a work-around. Not elegant and has its drawbacks, but basically it was log out, don't give co.com your OP number, book and buy the ticket as an "outsider," fill in all the address and credit card information that you normally don't have to when you are logged in, and once you have bought the ticket on line, then go to CO to give them your FF number.

Drawbacks: You don't get any priority seating, you don't get to click that you would like an upgrade if available.

So, I called Elite Priority Line and they did it for me. Very nice, but a bit cumbersome, I would say. If it is CO's aim to have as many bookings as possible on line, and cut down the staff time needed to book, then they should fix this particular glitch, since talking to the OP Elite line negated the cost advantages of booking on line.