• Turn off your laptop by holding the power down.
  • While holding the "Shift" key turn your laptop back on. (Booting to Safe Mode) When you see the grey Apple logo you can release the Shift key.
  • Login to your laptop - the screen will flicker.   Run any updates.  
  • Restart your computer (if the update doesn't.)
  • If your screen is still flickering you are still in safe mode.  Restart until it goes away.