I tried to pingback a post on another blog and it did not work. No error messages produced either.
Pingback sent from http://2fargon.com/beta/ which is now running the delta, to http://2fargon.com/wordpress/index.php?p=3 which is a demo blog.
You can login to both using the password "password" as the admin, if you want to test it.
You can use http://2fargon.com/beta for beta(delta) testing too, just don't change the password, please! :)