Snippets of WP Alchemy multidimensional code

wpalch_multi.php

<?php 
/**
 * I'm using WP Alchemy as a way to select images that have been pulled from a Pinterest board. 
 * As a result, each image has two properties: URL and Title.
 * All the examples for the Checkbox/Multicheckbox form type involve feeding a simple array into a loop of some sort: 
 */
?>
<?php $items = array('a', 'b', 'c'); ?>

<?php foreach ($items as $i => $item): ?>

   <?php $mb->the_field('cb_ex2', WPALCHEMY_FIELD_HINT_CHECKBOX_MULTI); ?>

   <input type="checkbox" name="<?php $mb->the_name(); ?>" value="<?php echo $item; ?>"<?php $mb->the_checkbox_state($item); ?>/> <?php echo $item; ?><br/>
	
<?php endforeach; ?>

<?php
/**
 * My $items array is necessarily multi-dimensional:
 */
?>

<?php
$items[] = array(
    'title' => 'A Title',
    'url' => 'http://something.com'
);   
?>

<?php
/**
 * ...With each image having its own array containing a title and URL. 
 *
 * My input thus looks like:
 */
?>

<input type="checkbox" name="<?php $mb->the_name(); ?>" value="<?php echo $item['url']; ?>"<?php $mb->the_checkbox_state($item['url']); ?>/> <?php echo $item['title']; ?><br/>


<?php
/**
 * However, I'm experiencing a weird bug where whatever's selected first persists across all posts
 * -- for instance, when I click to create a new post of this content type, the values I selected 
 * the very first time are pre-selected. I can't even change them in the first post, they just revert back.
 *
 * My guess is that passing an array key to the_checkbox_state(); like I've done is causing stuff to not work. 
 * Any thoughts? Thanks!
 */
?>