Comment 9 for bug 313231

My workaround now is to reboot and change the brightness from grub(!)

$ dpkg -l | grep linux-image
ii linux-image-2.6.24-19-generic 2.6.24-19.41 Linux kernel image for version 2.6.24 on x86/x86_64
rc linux-image-2.6.24-21-generic 2.6.24-21.43 Linux kernel image for version 2.6.24 on x86/x86_64
ii linux-image-2.6.27-11-generic 2.6.27-11.27 Linux kernel image for version 2.6.27 on x86/x86_64
ii linux-image-2.6.27-7-generic 2.6.27-7.16 Linux kernel image for version 2.6.27 on x86/x86_64
ii linux-image-2.6.27-9-generic 2.6.27-9.19 Linux kernel image for version 2.6.27 on x86/x86_64
ii linux-image-generic 2.6.27.11.14 Generic Linux kernel image
$ uname -r
2.6.27-11-generic
$ dpkg --status linux-image-2.6.27-11-generic
Package: linux-image-2.6.27-11-generic
Status: install ok installed
Priority: optional
Section: base
Installed-Size: 92184
Maintainer: Ubuntu Kernel Team <email address hidden>
Architecture: i386
Source: linux
Version: 2.6.27-11.27
Provides: fuse-module, ivtv-modules, kvm-api-4, linux-image, linux-image-2.6, ndiswrapper-modules-1.9, redhat-cluster-modules
Depends: initramfs-tools (>= 0.36ubuntu6), coreutils | fileutils (>= 4.0), module-init-tools (>= 3.3-pre11-4ubuntu3)
Pre-Depends: dpkg (>= 1.10.24)
Recommends: lilo (>= 19.1) | grub
Suggests: fdutils, linux-doc-2.6.27 | linux-source-2.6.27
Conflicts: hotplug (<< 0.0.20040105-1)
Description: Linux kernel image for version 2.6.27 on x86/x86_64
 This package contains the Linux kernel image for version 2.6.27 on
 x86/x86_64.
 .
 Also includes the corresponding System.map file, the modules built by the
 packager, and scripts that try to ensure that the system is not left in an
 unbootable state after an update.
 .
 Supports Generic processors.
 .
 Geared toward desktop systems.
 .
 You likely do not want to install this package directly. Instead, install
 the linux-generic meta-package, which will ensure that upgrades work
 correctly, and that supporting packages are also installed.