I have earlier today logged into my early 2011 MBP and running Yosemite without any issues. However, on booting up the MBP showed the login screen into which I entered my usual password, it then shows a progress bar below my login name and then shows a dialogue box stating: You are unable to log in to the use account "----------------" at this time. Logging in to the account failed because an error occurred. I have restarted it and used CMD R to restore from backup, but none are displayed. I have reset my login password, but to no avail. Please could someone, anyone help me with the above. I would rather not reinstall OS X as I will loose everything.