this bug affects the 11.10, to fix it, we need to change the /etc/defaut/grub in the line GRUB_CMDLINE_LINUX_DEFAULT="quiet splash" change to GRUB_CMDLINE_LINUX_DEFAULT="quiet splash acpi_osi=Linux acpi_backlight=vendor"
This issue affects Ubuntu 10.10, 11.04 and 11.10
this bug affects the 11.10, to fix it, we need to change the /etc/defaut/grub in the line GRUB_CMDLINE_ LINUX_DEFAULT= "quiet splash" change to GRUB_CMDLINE_ LINUX_DEFAULT= "quiet splash acpi_osi=Linux acpi_backlight= vendor"
This issue affects Ubuntu 10.10, 11.04 and 11.10