Won't Shut Down

Novice here...Running Win 8.
Laptop was working perfectly since purchase 4-5 months ago. Nearly instant startup & pretty quick shutdown.


As of Friday,when i shutdown my laptop - the screen, after a much longer wait, shuts down but the power button light (& lit up keyboard) still remains on.


Read elsewhere that holding the SHIFT key while clicking 'shut off' will work & IT DOES!!!
Any explanation and suggestions?