Ubuntu – Screen turn off/crazy when I adjust the screen brightness continuously on a Dell Studio 1558

I have a Dell Studio 1558, With a Mobility Radeon HD 4500/5100 Series on Unity 2D.

After a clean install of Ubuntu 12.04, I rebooted and logged in to my Ubuntu.The screen was too bright, So I press F4 to decrease the brightness. But when I pressed F4 repeatedly to decrease the brightness to 0, My Laptop screen turned off, I had to shutdown my laptop by pressing the power button.

So I tested it again few times and got the same result, I tried to install the Additional Drivers (ATI/AMD proprietary FGLRX), Tested it again, The screen didn't turned off but go crazy, And I still had to shutdown my laptop.

I think may be this is happening due to the F4 key, I install xbacklight and used it to dim my screen brightness. If I try to set xbacklight -set 50 and then 40-30… my screen still dead!

Not just the screen is dead, I must say the Laptop is dead, I can open any command prompt. Event when I try to close the lid, The Laptop doesn't suspend.

• Just tried to install Gnome-Shell, every thing seems to work OK!