Solution: Adding acpi_backlight=vendor to the kernel's parameter list in your bootloader should do the trick.
See http://www.voria.org/forum/viewtopic.php?p=4399#p4399 (some technical detail) and http://www.voria.org/forum/viewtopic.php?p=4409#p4409 (step-by-step instructions).
Solution: Adding vendor
acpi_backlight=
to the kernel's parameter list in your bootloader should do the trick.
See http:// www.voria. org/forum/ viewtopic. php?p=4399# p4399 (some technical detail) and http:// www.voria. org/forum/ viewtopic. php?p=4409# p4409 (step-by-step instructions).