dazzlesoftware on "plugin only works after I change priority"

Hello I seem to have issue well in my plugin it setup post types via config array which is attached via filter

add_action( 'init', 'headlines_register_post_type');
function headlines_register_post_type()
{
	$post_types = apply_filters( 'headlines_post_types', array() );
	foreach ( $post_types as $post_type )
	{
		new Headlines_Post_Type( $post_type );
	}
}

but as soon as I call my class function for

add_action( 'init', array( $this, 'register_post_type' ) );

it stops working but if I change the priory for

add_action( 'init', 'headlines_register_post_type', 5);

it works how can I use the default priory ? as I sure this is not good way to code plugins changing the priory as it could conflict other plugins maybe ...

Stephen