Pb javascript et IE

var champ=false;

function champsur(obj){
 champ=obj;
}
function selection(val){
 champ.value=val;
 champ.focus();
}

 <div id="saisie">
   <form id="creationclient" enctype="application/x-www-form-urlencoded" action="" method="post">
   <dl class="zend_form">
      <dt id="id-label">&nbsp;</dt>
      <dd id="id-element">
         <input type="hidden" name="id" value="" id="id" />
      </dd>
      <dt id="Types_clients_id-label"><label for="Types_clients_id" class="required">Type de clients</label></dt>
      <dd id="Types_clients_id-element">
         <input type="text" name="Types_clients_id" id="Types_clients_id" value="" onFocus="champsur(this)" />
      </dd>
      ... autres champs ...
      <dt id="submit-label">&nbsp;</dt>
      <dd id="submit-element">
         <input type="submit" name="submit" id="submit" value="Valider" />
      </dd>
   </dl>
   </form>
</div>
<div id="aide">
</div>

ma page insérée en ajax

<?php header("Content-type: text/plain; charset=UTF-8"); ?>
<table id="aide">
 <tbody>
  <?php
  foreach ($this->typesclients as $typeclient) {
   echo ' <tr onclick="selection('.$typeclient->id.')">';
   echo ' <td>' . $typeclient->id .'</td>';
   echo ' <td>' . $typeclient->designation .'</td>';
   echo ' </tr>';
  }
  ?>
 </tbody>
</table>