A script fail after adding the jquery ui tabs in the site

A script fail after adding the jquery ui tabs in the site

Hi,
 
I had just use the jquery-ui tabs to change the interface of the site, but after i apply it, i found the ajax function which works before had became fail. I would like to know will there be any way to fix the problem.
 
The script of ajax is below:
 
$(document).ready(function() {
 $('#usernameLoading').hide();
 $('#username').blur(function(){
   $('#usernameLoading').show();
      $.post("lib/check_username.php", {
        username: $('#username').val()
      }, function(response){
        $('#usernameResult').fadeOut();
        setTimeout("finishAjax('usernameResult', '"+escape(response)+"')", 400);
      });
     return false;
 });
});