llCollisionFilter isn't filtering

I'm having this huge problem that is just urking me!
I have made a small game where you control a ship from pad to pad. I have llCollisionFilter in the ship to have it explode if it touches anything other than "Landing_Pad" however no matter what it touches, ground and pad alike, it still dies. In the wiki it says to put empty Collisions in the parts that have no effect but that doesn't work either.
This is my first game using llCollisionFilter so what am I doing wrong?

landing pad is called "Lander_Pad"
llCollisionFilter("Lander_Pad", NULL_KEY, FALSE); Is under 'entry_event' and 'on_rez' and I have tried both FALSE and TRUE.

- Mike

Have it tell you what it collides with before it explodes. I found it unreliable, although it still filters out a lot of the collisions with objects other than the one you're interested in.

I'd use this:

explode()//Feel free to add in a llRezObject to spawn debris here, and maybe a llSetParticleSystem for an explosive particle effect.
{
    llPlaySound("Explosion",1);
    llDie();
}

default
{
    collision_start(integer num_detected)
    {
         if(llDetectedName(0)!="Landing_Pad")
         {
              explode();
         }
    }
}

[edit]
used the wrong logic gate in the if statement. do'h!