title: jQuery fadeOut callback error
body: <p>Firebug indicates I have a <code>TypeError: a.ownerDocument is undefined</code> with this code:</p>
  
  <pre><code>$(this).text('Updated!').fadeOut('900',  function() { 
    $(this).text('Update').attr('disabled', 'disabled').show()
  });
  </code></pre>
  
  <p>A more complete snippet follows:</p>
  
  <pre><code>$(".update-role").click(function() {
    var newRole = $(this).prev().val();
    var userId  = $(this).parents('tr').attr('id');  // e.g. 'user-role-18'
    userId = userId.split('-');
    userId = userId[2]; // so we get '18'
    $.getJSON('services/update_staff_role.php', {r: newRole, id: userId}, function(j) {
      if(j.result == 'success') {
      $(this).text('Updated!').fadeOut('900',  function() { 
            $(this).text('Update').attr('disabled', 'disabled').show()
          });
      } else {
        alert(j.reason);
      }
    });
    console.info(userId, newRole);
  });
  </code></pre>
  
  <p>Could it be because I'm using <code>this</code>, because I'm using a <code>callback</code> inside another <code>callback</code>? </p>