Every wondered why does you custom kernel parameters in /etc/sysctl.conf doesn't get set on startup even after you add sysctl -p on boot scripts?
The reason might be kdm. It happens that when a user logs in using KDM, it resets the kernel parameters to default, making the init scripts's parameter settings to non existent.
I've reported a bug on this, as an alternative you can set the kernel parameters after you've logged in by setting a timer in the start up script -
sleep 40; sysctl -p
A better idea will be automatic login; for security, you might configure kdm to lock screen after log in (this can be found in system settings > login screen).