problem with $.post

problem with $.post

Ok, so my $.post ajax query isn't going through and I can't figure out why. I've cut out almost everything, and boiled it down to only a really basic function, but still nothing. Here is the Client Side code:

<html>
<head>
<script type="text/javascript" src="jquery-1.4.2.js"></script>

<script type="text/javascript">
function cstarter()
{

window.einterval = setInterval("cst()", 5000);
window.big = "hi";
}
</script>





<script type="text/javascript">


function cst()
{


$.post("testback.php", { csize: window.big },
   function(theXML){
   $('label',theXML).each(function(i){
    
   window.creply = $(this).find("numb").text();
    window.cnumb = $(this).find("rep").text();
   
  
    });



$('.inner').append(window.creply);
$('.inner').append(window.cnumb);
}
);






}
</script>
</head>
<body>


<div class="inner" >
  
</div>

<script type="text/javascript">
cstarter();
</script>

</body>
</html>




And here is the serverside code:

<?php header('Content-Type: application/xml; charset=ISO-8859-1')?>
 


<?php
$cnumb = $_POST["csize"];

$ccrank = "$cnumb"."bye";
$ctest = "yeahhh";


echo "<?xml version=\"1.0\" encoding=\"UTF-8\" standalone=\"yes\"?>

   <label>
     <rep>$ccrank</rep>
     <numb>$ctest</numb>
   </label>

   ";

?>



Sorry about the mess, as I said it's a chopped up version of something much bigger. Anyway, any input would be much appreciated. Thanks.