Unable to log in to the user account "at this time"

Help... I cannot login to my macbook under my username - There is only 1 x username which is the administrator account. Error message reads - You are unable to log in to the user account "_________" at this time.

I've already changed passwords via the master password prompt - Reset PRAM - Removed battery, but still no luck...

I have no idea what to do now? Any suggestions?

Many thanks