I've just ran into an issue where an admin user can log into his account but once logged in and a password is somehow required, OS X says he's using the wrong password. The password doesn't have any weird characters, it's a low security password.
I've tried to boot from the install disk and reset the password, didn't work.
I've checked the permissions and repaired them, didn't work.
I've checked the disk, it was fine.
I'm really lost here, seems like the passwords are messed up in OS X, anyone have any idea how to fix this?