[Plugin: Invite Friends] jquery error

This is the bit that causes the error (in bp-invitefriends-admin.php5)

<script src="../wp-content/mu-plugins/bp-invitefriends/lib/jquery.js" type="text/javascript"></script>
<script type="text/javascript">
$(document).ready(function()
{
  //hide the all of the element with class msg_body
  $(".msg_body").hide();
  //toggle the componenet with class msg_body

  $(".msg_head").click(function()
  {
    $(this).next(".msg_body").slideToggle(600);
  });
});
</script>

if I remove it the ajax on the plugin settings page doesn’t work. any idea how I can fix this?