Comment 13 for bug 257827

I can confirm it on Hardy, running kernel 2.6.24-19-generic on Inspiron 1520.

I found that the problem is kernel related:
When pressing Fn+Up/Down once, `cat /proc/apci/event' gives every event twice. (Catting /proc/apci/event is possible only after killing acpid.)

Monitoring key presses with xev or showkey is of no use. I inspected acpid source code and it works like this:
- acpi event is generated by kernel
- acpid reads /proc/acpi/event and for every event read it runs a script (e.g. /etc/acpi/video_brightnessup.sh)
- this scripts runs acpi_fakekey with some argument that passes a synthetic key press to the X server
- X, KDE or Gnome (whatever takes the responsibility) runs an action bound to the key press

So, if the event is generated twice by kernel for one Fn+Up/Down key press, KDE's or Gnome's action is run twice.

What more information can I provide?