Backlight change = hard freeze
I have Lenovo T420 with Nvidia NVS4200 and Intel graphic. I use Nvidia only with binary drivers 280.13 (x86_64). I have vanila kernel 2.6.39. If I load nvidia kernel driver and touch brightness keys (fn + home or end) or touch /sys/class/backlight/acpi_video0/brightness via echo, my system locks up completely.
Is this a known problem? Is there any workaround?