All of a sudden it says password incorrect. I am 100% sure of my password. I don't know what happened. Hacked ?
Have you verified your password is correct by authenticating through the GUI? An easy way is to go to System Preferences > Accounts and click the lock icon. Also, verify that your user account has not lost administrative privileges (you can do this from the same preference pane). If you've lost administrative privileges the issue may be related to something else.