Acer TravelMate 4740 series laptop.
Brightness control keys (Fn+Right/Left) work on Windows 7, but not on Linux(tried both Ubuntu and Kubuntu).
Linux shows the brightness bar(bulb) when the keys are pressed, it even increases and decreases, but the brightness does not change.
Volume keys (Fn+Up/Down arrow) work perfectly in all OSs.
Any solution? I guess this is a hardware problem with Acer.