Probleem met javascript/jquery en mySQL/PHP

[Stabiloy]

Hallo,

Heb onderstaande code om een shoutbox op mijn site te plaatsen. Echter wilt de submit functie niet werken. Hoop dat één van jullie mij op weg kan helpen.
chatlist.php

$act = $_GET['act'];
	if ($act == "add"){
	  $nick = $_GET['nick'];
	  $msg = addslashes($_GET['msg']);
	  $sql = "INSERT INTO Forum_Shout (naam, shout, datum)
				   VALUES ('".$nick."','".$msg."','".time()."')";
	  $qry = mysql_query($sql)or die("fout");
	}
	$sqlLoad = "SELECT * FROM Forum_Shout ORDER BY datum DESC LIMIT 0,20";
	$qryLoad = mysql_query($sqlLoad);
	$rsLoad = mysql_fetch_array($qryLoad);
	
	echo '<table width="100%" cellpadding="0" cellspacing="0" border="0">';
	do{
		$i++;
		$u = $i % 2;
		if($u != 0)
		{
			$bg = ' bgcolor="#CCCCCC"';
		}
		else
		{
			$bg = '';
		}
		echo '
			<tr valign="top"'.$bg.'>
				<td>'.$rsLoad['naam'].'</td>
				<td>
					<img src="http://www.bryantan.info/uploads/jquerysamples/bullet.gif" />
				</td>
				<td>
					' .$rsLoad['shout'] . '<br />
					<span class="date">'.date('H:i:s Y-m-d',$rsLoad['datum']).'</span>
				</td>
			</tr>';
	
	}while($rsLoad = mysql_fetch_array($qryLoad));
	echo '</table>';

shout.php

<div id="chatbox">
    <form id="form">
    	<input type="hidden" value="<? echo $_SESSION["GyntoNaam"]->naam;?>" id="nick"/>
        <table>
            <tr>
                <td><label>Shout:</label></td>
                <td><input id="message" type="text" maxlength="255"/></td>
                <td><input id="send" type="submit" value="Shout it!" /></td>
            </tr>
        </table>
    </form>
	<div id="ajax">
    	<div class="acontent">
    		<div id="msg">
    
    		</div>
  		</div>
	</div>
</div>

En tot slot het javascript/jquery gedeelte.
[JS] $(document).ready(function(){

updateChatbox = function updateChatbox(){
$.ajax({
type: "POST",
url: "Includes/chatlist.php?",
data: "act=update",
cache: false,
success: function(html){
$('#msg').html(html);
}
});
}

updateChatbox();

$("#form").submit(function() {
nick = $('#nick').val();
msg = $('#message').val();
$.ajax({
type: "POST",
url: "Includes/chatlist.php",
data: "act=add" + "&nick=" + nick + "&msg=" + msg,
cache: false,
success: function(html){
$('#msg').html(html);
}
});
$('#message').val(""); // reset the value
return false; // return false to prevent loading the page
});

setInterval(updateChatbox, 1000 );
});[/JS]

Het updaten om de 1sec werkt op dit moment wel..