I did a system update yesterdy on Kubuntu 12.04 32 bit. Hardware is acer d270 with atom 2600/cedarview. Cedarview drivers installed through additional drivers and it worked before.
The brightness control no longer works with either the keyboard or through
System Settings -> Power Management. I can still change it by copying and pasting:
sudo setpci -s "00:02.0" F4.B=30"
into the terminal. This is very annoying.
Kernel was updated from 3.2.0-39-generic-pae to 3.2.0-40-generic-pae through muon updater. It asked me if I wanted to mark the changes for the kernel update. I did so, having done this in the past with no problems. This very well may have been a mistake.
I checked the grub config file to see if the
acpi_backlight=vendor parameter had been overwritten. It's still there. It may need a different parameter now, I have no idea.
The thing is, I found out how to bring up the grub menu on a single boot system and rebooted into 3.2.0-39. The brightness control still didn't work. This is, again, very annoying.