2010-11-09 I just got my laptop working properly again under Ubuntu 10.10! A small slip broke X windows after my initial work with Ubuntu 10.04.
This one had me guessing for a while. It took a friend's help to sort it out. I thought it was something to do with the X set up, but it turned out to be the 'nomodeset' which I had inserted into the grub option. This is OK under 10.04 (I think it helped, but can't remember exactly why I included it) but not under 10.10, it seems. Remove it before you upgrade to 10.10!
|7. ACPI Backlight option||-0.?W||
I added GRUB_CMDLINE_LINUX_DEFAULT="acpi_backlight=vendor" into /etc/default/grub, which allowed me to change the screen brightness again. To activate this, run "sudo update-grub" after editing.