This has occurred a number of times, with several partner airlines. We've retitled so we can keep track (and maybe resolve) some of these AA ticketed on other airlines that somehow fails.

It's happened with us (as mentioned above - we flew SFO-LAX and Lady JDiver was denied boarding by Iberia for our MAD flight. Similar issue, and we got it resolved just in time to fly. The Executive Platinum agent and a supervisors got the AA Liaison to Iberia to straighten it out, in our instance, but it took over a couple of hours at the TBIT ticket counter (couldn't check in on line).

I'm not sure why this happens on various airlines, I do know it happens. Perhaps it's partially because AA cancelled their development contract with H-P for a new PSS (Passenger Service System) (Jetstream) due to bankruptcy, or merely just because the systems don't play well together when one airline makes changes. But with the "new" AA choosing Sabre, given BA, CX, JL, QF etc. chose Amadeus Altéa, don't expect a quick or easy solution.

AA announces Jetsstream Aug 26, 2009: http://hub.aa.com/en/nr/pressrelease...service-system

June 2012 AA announces Jetstream is dead: http://www.flyertalk.com/forum/ameri...stem-dead.html