I just tried to use Online Checkin for flights tomorrow and it wouldn't let me because I have upgrades using CR-1s from a fellow Flyer Talker's account...she signed the authorization form at the airport..the error message I'm getting online is that the upgrades have "not been authorized by the Mileage Plus member."

How early can Mr. Easy Checkin at the airport be used? I've heard both 4 hours and 24 hours before flight...and am I likely to get the same error message there? (I have to go to the airport this afternoon to pick up my wife so would use the machine then for flights tomorrow)

I'm trying to avoid waiting in line for a counter agent tomorrow...