Eu instalei o Yosemite e não reconhece minha senha do usuário (admin).
sim - eu sou positivo que estou usando a senha correta.
Não - o bloqueio de caps é não on.
Qual é o problema?
I Installed Yosemite and it won't recognize my (admin) user password.
Yes - I am positive that I am using the correct password.
No - Caps Lock is not on.
What is the problem?
It will be hard to tell what has broken without being logged in, but the solution is easy.
Boot to the Recovery HD (power cycle the Mac, then hold Cmd-R until the screen goes grey. Then wait about a minute or so and you should get the recovery tools. See http://support.apple.com/kb/HT4718 for details) and reset the password to be what you want it to be. Once you get logged in again, you can look at the logs and patch up your Keychain as needed.
It may be related to https://discussions.apple.com/thread/6701865 which may be an Apple side bug. +1 it you think it is the same problem.
If you are using a network account, try turn off wifi/network about 30s before you shut the machine or leave it to sleep. (bit of a pain though)
The same thing happened to me. After a full day and night of struggling and trying every suggestion, I saw Apple made a "root admin" user on my computer that I didn't have knowledge of that superseded the admin account I made. So actually instead of typing my admin username, I typed in "root" as the username and it worked. Weird. Not sure how that happened.