Screen Brightness controls not working.

The sven keyboard daemon, which is in the system tray, calls a couple scripts to control the screen brightness. Unfortunately this varies a bit between computers. There's a couple things that can go wrong with this.

1) Sven isn't configured to use the correct keys for your computer.

2) The two scripts that Sven calls (/usr/bin/brightness-up and /usr/bin/brightness-down) could be using the wrong file in /sys

So the first thing to do is open a terminal and type:
brightness-up and then press Enter.

If it changes the screen brightness then it's probably problem 1, and you need to right-click on the sven tray icon and select Preferences. If you get an error about file not found , then it's probably problem 2.

The brightness-up script looks like this:
DEVICE= #radeon_bl0, acpi_video0, etc

[ -z $DEVICE ] && DEVICE=$(ls $DEVPATH | head -n 1)
[ -z $DEVICE ] && exit 1

CURRENT=$(cat $DEVPATH/$DEVICE/actual_brightness)
MAX=$(cat $DEVPATH/$DEVICE/max_brightness)
if [ "$CURRENT" -gt "$MAX" ]; then CURRENT=$MAX; fi
echo $CURRENT > $DEVPATH/$DEVICE/brightness

For problem 2, you'll need to replace /sys/class/backlight/acpi_video0/ with the correct path. You'll also need to make the corresponding changes to /usr/bin/brightness-down.