Happened to me this last night as well. Flew from LAX-JFK-GIG. Arrived this morning, tried to login into my account right now. Unable to authenticate myself. Went to my mail e-mail box and saw the "security" warning and a new AAAdv account number. Tried to get a password for the new account without success.
I don't have any US airways account. When logged to my account some 40 hours ago to select my seats, the web site automatically directed me to an ok button to merge AA/US accounts. Big mess, member since '96, appears to be a very very serious and massive problem. Unable to see the status of my upgrades.
