not sure if this effects just the air or all mountain lion but i discovered a bug. in mountain lion it places your full name in the menu bar up top. I thought maybe i should remove my last name in case i ever took a desk screenshot and forgot about it my full name wouldnt be there. so i clicked my name in the bar up top and chose user groups. from here i simply trimmed off my last name. this worked. however, when my machine went to sleep and woke up again, it had my full name as a log in and my password didnt work anymore because it had my last name. it took me awhile to figure out what was happening because my password wouldnt work and i knew it was the right one. then i hard reset to reboot and when the log in came up again this time it only had my first name and the password worked. so anyway. if anyone changes their name the first time it goes to sleep and wakes up it will have the old value and your password wont work.