Hi,
As described on title, due to security reasons my web server has /wp-admin folder password protected for web access, so every post load or homepage load tries to access jQuery on /wp-admin/admin-ajax.php so I'm asked for user and password (web based password), if logged in it doesn't ask. So normal users are prompted for a user/pass every time they load a post or the homepage, if they cancel they can see the posts but, and worst of all, no data is collected.
I think this has no solution, but I prefer to ask before deactivating the plugin, thanks!
http://wordpress.org/extend/plugins/wordpress-popular-posts/