Windows 8 on ASUS notebook, brightness down does not work

Recently my brother installed Windows 8 on his ASUS notebook. He had problems with the FN keys, so he asked me to have a look at it.

I've installed the ATK Package from ASUS found in this other question. This package fixed the problems I had with my own notebook, so I thought it would work for my brother too. However, on his notebook there is still one hotkey that does not work: brightness down (FN+F5).

Whenever that hotkey is pressed, it will only turn the brightness down one step, and after that all hotkeys suddenly stop working. It seems like the entire hotkey driver freezes. After a while (30s to 2m) the on-screen notification from the brightness change suddenly pops back up, and everything seems to work fine again. That is of course until I press FN+F5 again. Strangely, brightness up (FN+F6) works just fine.

I already tried reinstalling both ATK drivers and NVIDIA video drivers, but that did not solve it. I've googled around, and found at least 3 other forums with multiple people experiencing the same problem, with no solution either.

Since I couldn't find anything related on superuser, I'm asking it here. Do you guys have any suggestions on how to solve this problem?

I had the same problem and had to resort to drivers form Asus Australia to solve my problem.

The mentioned drivers package is ATKPackage_Win7_32_Z100014, which can be accessible, among other locations here.