AJAX, fonctionne pas IE, mais ailleur oui

<?php 
chdir('../'); 
require_once('./librairies/final.php'); 
Standard_Header('Trouver une ville', true, true, true); 

header('Pragma: no-cache'); 
header('Expires: 0'); 
header('Last-Modified: '.gmdate("D, d M Y H:i:s").' GMT'); 
header('Cache-Control: no-cache, must-revalidate'); 
header('Content-type: application/xml'); 

if($User->is_loaded() == true){ 
 if(isset($_REQUEST['q']) == false OR isset($_REQUEST['sid']) == false){ 
  $_REQUEST['q'] = null; 
  $_REQUEST['sid'] = null; 
 } 

 $What = $_REQUEST['q']; 
 $Sid = $_REQUEST['sid']; 
 $Render = (string)null; 

 if($What != null AND strlen($What) > 3 AND is_numeric($Sid)){ 
  $queryResults = $Query->query_locations('SELECT  DISTINCT ('loc'.'city'), 'loc'.'country', 'loc'.'region', 'country'.'printable_name' FROM 'locations' AS 'loc' LEFT JOIN 'country' ON ('country'.'iso' = 'loc'.'country') WHERE 'loc'.'city' LIKE "'.$User->escape(format_url($What)).'%" ORDER BY 'loc'.'city' LIMIT 0,7 ', __LINE__); 
   
  if(mysql_num_rows($queryResults) > 0){ 
   $Render = '<ul style="width: 200px;  list-style-type: none; overflow:auto; height: 70px; clear:both;">'; 
    
   $i=0; 
   while($resResults = mysql_fetch_assoc($queryResults)){ 
    $i++; 
    $onClick = 'document.getElementById(\'id_ax_adrs_city\').value=\''.addslashes(htmlentities($resResults['city'])).', '.htmlentities($resResults['region']).', '.htmlentities($resResults['printable_name']).'\'; document.getElementById(\'livesearch_city\').style.display=\'none\'; return false;'; 
     
    if($i==1){ 
     $Render .= '<li style="width: 175px; border: 1px solid #000000; background-color: #EEEEEE; margin-bottom: 4px;">'; 
    } 
     
    $Render .= '<span onclick="'.$onClick.'"'.($i==1 ? ' style="padding-right: 10px;"' : '').'><strong><a href="#" onclick="'.$onClick.'">'.htmlentities($resResults['city']).'</a></strong>, <em>'.htmlentities($resResults['region']).', '.htmlentities($resResults['printable_name']).'</em></span>'; 
     
    if($i==2){ 
     $Render .= '</li>'; 
    } 
     
    if($i=2){ 
     $i=0; 
    } 
    $onClick = null; 
   } 
    
   $Render .= '</ul>'; 
  } 
 } 
 else { 
  $Render = null; 
 } 
} 
else{ 
 echo 'Erreur'; 
 exit(); 
}  

echo $Render; 
Standard_Footer(true); 
?>