AJAX calls fail when the base URL is set I have installed the Drupal 7.17 security update, and I am having some issues with my site. 

If I comment out the $base_url ='www.xxx.com'; line in the setting.php file, the AJAX calls work; when I uncomment that line, the AJAX calls fail.

What could be the reason behind this? how can I get my base_url working again?
Make sure you didn't already include a base URL in your ajax link. For my development site, http://localhost/project1/ajaxlink, the following will work perfectly when no base URL has been set.

$.ajax({url: 'project1/ajaxlink', ...


In case a base URL has been set, the AJAX call is equivalent to the following, which will not work.

$.ajax({url: 'project1/project1/ajaxlink', ...