It may well be the web site just cannot work with a 14 Digit E-Ticket number. Most E-Tickets are 13 digits but I know there are exceptions and some are 14 digits too.

The only other real alternative if you cant get in with an e-ticket number is create an Asiana Club account, get your Asiana booking reference by calling Asiana (and getting seat assignments while you are on the phone asking for the booking reference ) and then log in with the Asiana booking reference and Asiana Club account number.

The only caveat doing it that way is the Asiana Club account must be created according to the same rule that the middle name or middle initial must be appended to the first name if either exist in the reservation since there is no place to put a middle name on flyasiana.com.

It only uses the Asiana Club number to look up your name. It doesn't actually use the number for the flights so you can get in that way even if you still intend to book the miles for the flight to some other airline.

And as always, only works in MS Internet Explorer.

And you can do OLCI 48 hours before booking and bag some previously blocked seats. In Y I have got bulkhead (but not exit row) seats that way. It changes often and is very dynamic during the 48 hour window so I usually check back often after first checking in.