I updated my Ubuntu to 11.10 a few hours ago and the screen brightness keeps going up to the maximum and down to the minimum all the time on it's own. Sometimes it stops for a few minutes. And when I try to set it myself manually or when a few minutes has passed, it starts up again. (I'm new in trying to fix my own problems, so I might not get the obvious things right away.)
I now restarted a couple of times and now I'm using a newer version of kernel and the brightness is now constantly down and can't be set manually.
My laptop is a Samsung N220. I bought it a little over a year ago. I still have Windows 7 Starter on it (it was originally on it), but I had Ubuntu put on it from the start.