Need Help With WP_Query (sort order)

I keep killing my site when trying to modify the arguments in a WP_Query

If I try to add a sort order such as:

'orderby' => 'title'

To the arguments, then the site crashes.

Here is how I am passing the arguments:

$args = array(
        'post_parent' => $post->ID,
        'post_type' => 'page'
        'orderby' => 'title'
    );
    $subpages = new WP_query($args);

But if I leave it OUT of the arguments, then It won’t crash. For example, it works fine if I just do this:

$args = array(
        'post_parent' => $post->ID,
        'post_type' => 'page'
    );
    $subpages = new WP_query($args);

But once I add ‘orderby’ => ‘title’, the site and the admin crash (just a white screen, no source is output to the screen at all).

And yes, I am trying to return pages, not posts.

I really am not sure what is going wrong.

If it helps, I am trying to use this whole bit of code for displaying child pages and their descriptions. The entire bit of code is:

function subpage_peek() {
    global $post;  

    //query subpages
    $args = array(
        'post_parent' => $post->ID,
        'post_type' => 'page'
    );
    $subpages = new WP_query($args);  

    // create output
    if ($subpages->have_posts()) :
        $output = '<ul>';
        while ($subpages->have_posts()) : $subpages->the_post();
            $output .= '<li><strong><a href="'.get_permalink().'">'.get_the_title().'</a></strong>
                        <p>'.get_the_excerpt().'<br />
                        <a href="'.get_permalink().'">Continue Reading ?</a></p></li>';
        endwhile;
        $output .= '</ul>';
    else :
        $output = '<p>No subpages found.</p>';
    endif;  

    // reset the query
    wp_reset_postdata();  

    // return something
    return $output;
}

add_shortcode('subpage_peek', 'subpage_peek');

// displays category descriptions as well as names - call with desc_cats()

function desc_cats(){
foreach (get_categories(array('hide_empty'=>true)) as $category)
{
$catid = $category->cat_ID;
echo '<li><a href="' . get_bloginfo('wpurl') . '/' .  $category->category_nicename . '/">' .
	$category->cat_name . ' (' . $category->count.$numposts.')</a>' . category_description($catid) . '</li>';
}
echo'<p>'; // puts a paragraph tag after last category description listed
};