I posted earlier that I saw a 764 appear on the p.s. schedule between two existing flights. Got a confirmed seat in Business Saver and a couple days out the flight was cancelled and I was automatically put in Y on a later flight. Funny thing is that the next flight out just switched from the 752 to 764 yet it has been J0 since it was up-gauged. Called UA and they couldn't confirm me into Business on the 764 even with 11 more seats in J, which filled up somehow (maybe with paid J pax from my flight).