If you need to switch a WordPress custom post type from post capability to page capability, do this.

change-cpt-to-page.php

<?php
/* This doesn't work and here's why not. 
 * 
 * The missing piece here has to do with rewrite rules. 
 * The registration process creates new rewrite rules during the process. 
 * This ensures the custom post type is set up appropriately.
 * Modifying the url structure (which we're doing here) to hierarchical requires a change to the rewrite rules as well.
 *
 * The following is the first change you need to make. The rewrite change is not included here. 
 */
// CAUTION! This could really ruin things, if you're not careful or aware of the changes this makes.
// Change `your_post_type` in line 6 to be the post type you're targeting.
// You may want to change $supports on line 12 to accommodate the custom post type's original functionality.
function change_cpt_to_page( $post_type, $post_type_object ) {
	if ( 'your_post_type' != $post_type )
		return;

	$post_type_object->hierarchical = true;
	$post_type_object->capability_type = 'page';

	$supports = array( 'title', 'editor', 'author', 'thumbnail', 'excerpt', 'page-attributes' );
	add_post_type_support( $post_type_object->name, $supports );

	global $wp_post_types;
	$wp_post_types[$post_type] = $post_type_object;
}
add_action( 'registered_post_type', 'change_cpt_to_page', 99, 2 );