Problem with collisions for player

I have a player running around in a maze. With the following settings he collides with the wall, but nothing else

Send Collisions
Receive Collision
Send Physics
Receive Physics

If I turn any of these off I no longer collide with the walls. The walls are done by painting tiles with collision set on.

The problem is, I can't collide with my npcs or enemies. Everyone has polygon collision masks, and the npcs and enemies detect when I shoot a bullet at them using the following code...

// Turn on collision, but turn off physics
   %this.setCollisionActive( true, true );
   %this.setCollisionPhysics(false, false);
   %this.setCollisionCallback(true);

.. and npcs detect the walls too. I just can't collide with them with my character. What's the trick?