Connection to the database has not been successful or your session has ended - try logging in again.
If the problem persists - Try changing the personal security on your internet browser to 'medium high'.
There is a possibility that your personal internet security set to 'high' which blocks the program from temporarily storing the login details on your computer.
Instructions to change browser settings:
From your browsers task bar click on: tools -> internet options -> protection of personal information
then set the slider bar to 'medium high' .