I got this problem with brightness on my fresh xubuntu 13.10 install..
It ain't inc/decrease the screen brightness when pressing Fn+F5/F6 !!
I've tried some solutions like setting these values in the /etc/default/grub file and sudo updating grub (this worked for me on my previous xubuntu 13.04 install)
GRUB_CMDLINE_LINUX_DEFAULT="quiet splash acpi_osi=Linux acpi_backlight=vendor" GRUB_CMDLINE_LINUX="acpi_osi=Linux acpi_backlight=vendor"
But still not working though :/
I have got a Sony VAIO VPCEJ3B1E running xubuntu 13.10 x64bit and an NVidia GeForce 410M and using the propritory drivers 319
Thanks in advance!