Screen brightness: can't adjust it

I can’t adjust the screen brightness on my Sony Vaio laptop. It’s too dark now; no difference between battery power and AC power.

This problem is new in 11.1: in 11.0 I could easily adjust the screen brightness with gnome-power-manager (brightness applet). I installed gnome-power-manager (brightness applet) in 11.1, but the applet doesn’t do anything.

I also installed spicctrl, but running it gives this error message:
@linux-satv:~> spicctrl -b 255
/dev/sonypi: No such file or directory

These are the hardware specifications of my laptop:
Sony Vaio VGN-BX296VP
Pentium M 1.6 Ghz processor
1 Gb RAM
Intel 915 video chipset (using 256 MB shared memory)
15.4 inch screen

Any help is welcome.

Greeting, Pjotr.

bump… anyone?