I found this possible solution for a dark screen on my Asus eee PC netbook
almost by accident.

I have been trying several distros of Ubuntu wondering which would work best
for me. Some gave me a very dark screen, to dark to even examine. The versions
I had problems with are Ubuntu 10.04 desktop and Ubuntu 10.10 netbook, this is
with either running on a HDD or USB stick. The dark screen may be an issue in
other versions as well.

The solution that worked for me is go to the System tab > Preferences > Power
management. On the tab marked "AC Power" you will see toward the bottom an area
marked "Display". Bellow this title will be a slider to sent the display
brightness. In the installs I have done, it is all the way to the right at
100%. Here is where it gets weird. Move the slider to the left, the screen
will darken, as you think it should, then when the slider moves past 80%, the
screen gets lighter, much brighter than it was at 100%. Choose the spot where
the screen is most comfortable for you, then click "Close" and you are done.
Your screen is now bright enough to read with ease. Every distro I have had a
dark screen this has solved the problem.