laptop brightness control problem

Hi guys, i am facing this weird problem today. It happened suddenly without me doing anything like update or messing with drivers. It happened all by itself.
My laptop brightness is locked. I am used to hotkeys (shortcut) to change brightness, When i press them now.. i see a bar which won't go up or down, it's locked and brightness too. I went to "Power Options" page via control panel, and i altered the brightness slider but it didn't help.
Any suggestions??

Things i tried..
-Restarted Pc..... nothing
tried to fix using this post.... http://www.eightforums.com/drivers-...ess-wont-adjust-after-windows-8-1-update.html
-I tried to update Intel HD Graphics 4000 driver but it says it's up to date.

Try booting is Safe Mode. Then go into Device Manager. Delete the video drivers. Reboot normally.

Windows will reinstall the driver that was already in use before you deleted it. But I have seen this "support trick" work with many different hardware components.

It is very low risk so even if it doesn't work it was worth a shot.