Error when logging out

[FAST50]

When logging off my forum we see this message:
"An error occurred while attempting to log you out. Click here to log out."

When you click that link, the next message says something like: Logged out. All cookies cleared. ..and all is well.


I found this code at the beginning of my header.
Could this be the cause of my log out problem?

 
<script type="text/javascript">
<!--
function log_out()
{
 ht = document.getElementsByTagName("html");
 ht[0].style.filter = "progid:DXImageTransform.Microsoft.BasicImage(grayscale=1)";
 if (confirm('$vbphrase[sure_you_want_to_log_out]'))
 {
  return true;
 }
 else
 {
  ht[0].style.filter = "";
  return false;
 }
}
//-->
</script>

Thanks for your help.