I have 3 users on my iMac. At the login screen it seems to accept password and the re-displays the login screen. I can't get past the login screen. No one has changed the passwords.
Can anyone help?
Is your computer plugged into an external monitor by any chance?
OS X 10.7 Lion /10.8 MountainLion
Follow the instructions in the first and the third boxes.
Retrieving data ...