I have an Dell Studio 1558, with a Mobility Radeon HD 4500/5100 Series.

After a clean install of Ubuntu 12.04, I reboot it.
And just like normal, I logged in my Ubuntu. And just like normal, the screen to bright, so I press "F4" to dim down the display. But when I press F4 again and again immediately (to dim down the brightness to 0), my laptop screen is turned off, I must shut down my laptop by pressing the power button!

So I test it some more time and get the same result, I try to install the Additional Driver (ATI/AMD proprietary FGLRX), test it again, the screen not turned off but go...crazy, and I still need to shutdown my laptop.

So I think this may due to the F4 key, I install "xbacklight" and use it to dim down my screen...when I try:
Code:
xbacklight -set 50
xbacklight -set 40
xbacklight -set 30
xbacklight -set 20
xbacklight -set 10
xbacklight -set 0
I try to run these command as fast as I can (set and reset) and it still make my screen go crazy!


Is this a bug?
Is there any one get the same issue with me?