Comment 19 for bug 172985

thinkpad-acpi module causes a seconed event (sudo acpi_liste), you could disable the brightness events while doing:
sudo -s
echo 0xfF00FFF > /proc/acpi/ibm/hotkey

Remember: after every reboot hotkey-setup echos another mask into hotkey

if you want to hack further stop hotkey-setup from doing this or file a bug against hotkey-setup