Hi, I've googled for this issue and i've found many potential solves of my problem: - Turning off adaptive brightness - disabling Light sensor in Device Manager - deleting SensorsAlsDriver.dll Nothing works. I'm actually using Win 8.1 Pro x64 with the newset updates. It is fresh-installed via bootcamp manager. After sleeping and waking up my Mac brightness buttons magically start working! What do I suspect? When i delete SensorsAlsDriver.dll and uninstall Proximity sensor in Device Manager, after reboot Windows re-installs the sensor, and re-apply the .dll file. I dont have an idea how to prevent OS from doing it...and I think it is potential solution. I've also found out that after installation of windows everything is ok. Although I'd like to have a up to date system... Could someone help me solving this problem?