Can't change brightness on HP Compaq 6715b laptop

[Klistvud <quotations@aliceadsl.fr>]

Hiya,

since I installed my fresh Lenny system several days ago, this thing has been 
bugging me: although the brightness buttons "work", ie the brightness 
slider/icon appears onscreen, it has no effect - the brightness of the LCD 
screen remains the same regardless of where I slide the brightness slider. 
Ditto when I unplug the power cord: the laptop automatically changes power 
schemes and the slider/icon appears onscreen for a second, showing different 
slider levels, but the brightness as such does not change a bit.

Anyone bumped into this bug before?

-- 
Registered Linux User 481801 and proud of it