Kubuntu 13.04 brightness problem with Nvidia GT425M

view story

http://askubuntu.com – I upgraded to Kubuntu 13.04 yesterday and after that the brightness changing function is not working. Before this operation, I was running Kubuntu 12.10 with additional driver for Nvidia GT425M. Brightness changing worked well all the time. (After changing grub file into this: GRUB_CMDLINE_LINUX_DEFAULT="quiet splash acpi_osi=") When I found brightness changing didn't work, I searched on the Internet and changed grub file into: GRUB_CMDLINE_LINUX_DEFAULT="quiet splash acpi_osi=Linux acpi_backlight=vendor" and GRUB_CMDLINE_LINUX_DEFAULT="quiet splash acpi_osi=Linux". Failed in both cases. I v (HowTos)