Ha Ha Ha
Heh - The same thing has happened to me too actually... Today actually! I was EUA 4 days out on IAH-SEA (flight 1065 10/30) and I selected 1A online after i got the upgrade, but then I checked in and I was moved to 6A!
(yes it was a 757-200 also) I've snagged 1A previously and kept it, so who knows what the deal is .. maybe it's Continental's way of playing mind games with us!
-Vincent