Can't adjust screen brightness in Lucid

[Marcelo Magno T. Sales]

Hello,

In Lucid's KDE, I can't adjust screen brightness on my Sony VAIO 
VPCF111FB laptop, neither using the Fn keys nor using the battery 
monitor plasmoid.
However, I can do it when running gnome using gnome's battery monitor 
widget. Also, in gnome the Fn keys activate the OSD which indicates 
screen brightness level, but they do not change the brightness level. In 
KDE, the Fn keys do nothing.
Anything I can do to adjust screen brightness in KDE?

Thanks,

Marcelo