Most of the time when this error occurs it is your CMOS settings deleating everytime you shut down.
Your CMOS settings is a very small memory in your MOBO that stors your bios setting (Time,Date, Video Settings, est)
When the battery on your motherboard goes dead, these errors occur.
Generally the CMOS Batteries recharge when you start your computer but there are still problems that occur (Happened to me once)
1st- Restart yout computer and enter you BIOS screen.
2nd- Load default settings , save and exit.
3rd- restart your computer and see if these changes corrected the problem.
4th- if problems persist, try buying a CMOS Battery at a local PC Shop
5th- Load battery, load defaults, restart and try again.