Found another post that handles this problem: http://ubuntuforums.org/showthread.php?p=9517612 ...and another hint that the bug might be in the kernel: /sys/devices/virtual/backlight/acpi_video0/brightness doesn't set the brightness.
Found another post that handles this problem: http:// ubuntuforums. org/showthread. php?p=9517612 virtual/ backlight/ acpi_video0/ brightness
...and another hint that the bug might be in the kernel: /sys/devices/
doesn't set the brightness.