very dimmed screen sometimes

I have reported this error before, but thought that I had it figured out but it was only partly.
I am running Ubuntu 11.10 on my old HP laptop.

When I leave the laptop on power unattended it goes into a sleeping mode despite the fact that I in setting have specified that it should not suspend.

When I try to start the laptop again it starts, but the screen is so dimmed that you can't do anything. I will thenn have to force a shut down by holding the power switch off for a time.
I might have to do this a couple of times before I finally manages to get the laptop going again.

Sometimes I have managed to get in to the Screen icon (System settings - screen) and put the glider back to max light.

I have then used a trick, namely to suspended be fore leaving the laptop. I have to leave the lid open though. If I close the lid then I will have the dimmed screen problem as descibed above.

When I restart, after having had the lid open, the laptop restarts fine.

I have considered to reinstall the whole system but I do not know if there are more intelligent solutions to my problem?