Collision response

I may be having another "doh!" moment here, but my objects don't respond when they collide. The callback function is getting called, because it spews object ids to the console just like I tell it to. :) Is there something else to turn on to get collision responses from the physics system?

I assume leaving off the collisionPolyCustom() will default to the quad, which is what it looks like is happening, so I don't think that's the problem.

//
	// Test ball
	//
	datablock fxImageMapDataBlock2D( ballImageMap )
	{
		mode = cell;
		cellWidth = 24;
		cellHeight = 24;
		cellCountX = 8;
		cellCountY = 5;
		textureName = "~/client/resource/balls/Pillbug/images/pillbug";
	};
	$ball = new fxStaticSprite2D() { scenegraph = t2dSceneGraph; };
	$ball.setPosition( "0 0" );
	$ball.setSize( "3 3" );
	$ball.setImageMap( ballImageMap );
	$ball.setFrame( 19 );

	$ball.setLayer( $LAYER_PLAYFIELD );
	$ball.setGroup( $COLLISION_GROUP_BALL );
	$ball.setCollisionPolyPrimitive( 16 );
	$ball.setCollisionActive( true, true );
	$ball.setCollisionMaterial( projectileMaterial );
	$ball.setCollisionMasks( BIT($COLLISION_GROUP_PLAYER) | BIT($COLLISION_GROUP_BRICK) | BIT($COLLISION_GROUP_TOTEM), BIT($LAYER_PLAYFIELD) );
	$ball.setCollisionCallback( true );

	$ball.setWorldLimit( bounce, "-50 -35 50 35" );
	$ball.setLinearVelocityY( -40 + ( getRandom() * 80 ) );
	$ball.setLinearVelocityX( -40 + ( getRandom() * 80 ) );

// Player 1 setup.
		$player1.setPosition( "-35 0" );
		$player1.setImageMap( jackImageMap );
		$player1.setSize( "8 8" );
		$player1.setWorldLimit( clamp, "-50 -35 50 35" );
		
		$player1.setGroup( $COLLISION_GROUP_PLAYER );
		$player1.setLayer( $LAYER_PLAYFIELD );
		$player1.setCollisionActive( true, true );
		$player1.setCollisionMaterial( standardMaterial );
		$player1.setCollisionMasks( BIT($COLLISION_GROUP_BALL), BIT($LAYER_PLAYFIELD) );

function fxSceneObject2D::onCollision( %srcObj, %dstObj, %srcRef, %dstRef, %time, %normal, %contactCount, %contacts )
{
	echo( "COLLISION: " @ %srcObj @ " hit by " @ %dstObj );
}