Popup comments goes to a blank page

In wordpress version 1.5 I try to set popup comments, and this is the result (I’m really bad, yes, I know), here:

https://www.blogdiscount.org/mokelembembe

The window opens correctly, but when you post a comment, the window goes not to the popup again, but on nothing, a nice white nothing page.
If I just add the common popup line in the index.php, it’s different: when you post a comment in the popup window, it goes to the permalink page (post+comments).
If I change also the last lines in the wp-commentspost.php, ok, the first I said is the result.

Oh oh, thank you for answering.
(sorry for my english)(this is a two hour work, uh)