@darkpaniel: Then you missed something
. What you describe sounds like an SO (Special Offers) device, in which case the only recommended way to get rid of it is to pay the fee to unsubscribe from SO in your 'Manage Your Kindle' page @ Amazon. Once your device is no longer part of the Special Offers program, this hack will function as expected, but not until that.
On the other hand, if you're British, and this is a device bought from Waterstones, keep reading
.
The easiest way to control the hack settings is through the KUAL extension that's automatically installed alongside the hack, so I'd recommend you look into how to setup KUAL, by checking out
this sticky thread.