front-end ajax form plugin

Hi,

I’m having some brain freeze getting around building a plugin that updates the database in some custom fields:

<?php
/*
Plugin Name: Ajax Playlists
Plugin URI: http://URI_Of_Page_Describing_Plugin_and_Updates
Description: A brief description of the Plugin.
Version: beta 0.1
Author: seb
Author URI: http://URI_Of_The_Plugin_Author
*/
?>

<?php function playlist_jquery() { ?>

<script type="text/javascript" language="javascript">
$(document).ready(function(){
	$("#submit").click(function(){
	$(".error").hide();
		var hasError = false;
		var playlist_nameVal = $("#playlist_name").val();
		if(playlist_nameVal == '') {
			$("#playlist_name").after('<span class="error">You forgot to enter a playlist name.</span>');
			hasError = true;
		}
		if(hasError == false) {
			$(this).hide();
			$("#submit.button").append('<img src="<?php bloginfo('stylesheet_directory'); ?>/images/ajaxloader.gif" alt="Loading" id="loading" />');
			$.post("<?php echo admin_url('admin-ajax.php'); ?>", $("#MakeNewList").serialize());
		}
		return false;
	});
});
</script>
<?php } ?>

<?php
add_action('wp_ajax_playlist_jquery', 'playlist_insert');
?>

<?php function playlist_insert() {

$table_name = $wpdb->prefix . "playlist_master";
$playlist_name=$_POST['playlist_name'];
$description=$_POST['description'];
$setuserid=$_POST['setuserid'];
$setadate=$_POST['setdate'];

$insert = "INSERT INTO " . $table_name .
            " (playlist_name, user_id, description, date) " .
            "VALUES ('" . $playlist_name . "','" . $setuserid . "','" . $description . "','" . $setadate . "')";

global $wpdb;
$results = $wpdb->query( $insert );
die();
} ?>

<?php
add_action ('wp_footer', 'playlist_jquery');
?>

the form on my page looks like this:

<form action="" method="post" id="MakeNewList">
Playlist Name:<br /><input type="text" name="playlist_name" id="playlist_name" /><br />
Playlist Description:<br /><input type="text" size="25" name="description" id="description" /><br />
<input type="hidden" value="<?php echo $getmother;?>" name="setuserid" />
<input type="hidden" value="<?php echo $CurDate;?>" name="setdate" />
<input type="submit" name="submit" id="submit" class="button" />
</form>

This works if I choose to put everything on the same page. Looking at firebug, the only response i get is a 0.

I have a sneaking suspicion that $.post("<?php echo admin_url('admin-ajax.php'); ?>", $("#MakeNewList").serialize()); is the culprit here. I just don’t have the mental capacity right now to see why.