Need help sorting posts from query_posts using meta_key and meta_value

I’m creating a theme with the option to create an online store. One option that needs to be included is a sort feature (i.e. priced low to high, high to low, a-z, etc.). The following code is what I worked up:

<?php
	// Let's start by checking the URL for variables
	$page  = $_GET['sort'];
	// Let's sort the store posts
	if ($page == false) {}
	elseif ($page == 'low-to-high') {
		query_posts('meta_key=price&meta_value=&order=ASC&cat=' . $category_id);
		}
	elseif ($page == 'high-to-low') {
		query_posts('meta_key=price&meta_value=&order=DESC&cat=' . $category_id);
		}
	elseif ($page == 'a-z') {
		query_posts('orderby=title&meta_value=&order=ASC&cat=' . $category_id);
		}
	elseif ($page == 'z-a') {
		query_posts('orderby=title&meta_value=&order=DESC&cat=' . $category_id);
		}
	// The Loop
	if(have_posts()): while(have_posts()): the_post();
	?>
		<div id="post-<?php the_ID(); ?>" <?php post_class(); ?>>
			<a href="<?php the_permalink(); ?>" title="<?php the_title(); ?>"><?php include(TEMPLATEPATH . '/thumb.php'); ?><span><?php the_title(); ?></span></a>
			<?php if(get_post_meta($post->ID, 'Price', true)) {
				echo '<div id="cat-price"><strong>Our Price:</strong>&nbsp;<span>' . get_post_meta($post->ID, 'Price', true) . '</span></div>';
			} ?>
			<?php edit_post_link( 'Edit', '<span class="the-edit">', '</span>' ); ?>
		</div><!-- id="post-<?php the_ID(); ?>" -->
	<?php
	endwhile; else: endif;
	wp_reset_query();
	?>

It seems to be missing something because when i try to sort using the META_KEY and META_VALUE, the order is incorrect (the order to its own child-category is correct but not on the parent category).

I’m not sure if I’m explaining this correctly and hope someone understands and can help.

Basicly: If I try to order the posts by the meta_key and meta_value, the output is incorrect in out of order.