TOPIC: HTTP Error 500 (Internal Server Error) on success.php

I've found out that if one follows the advice here:
http://docs.joomla.org/Moving_sensitive ... e_web_root
(which I have done on all my Joomla installs over last couple of years)
The com_dtregister/success.php file gives an Internal Server Error.

This is down to line 56 and 57 that assume configuration.php and defines.php are in the default position.
If one changes the path on these two lines the Error 500 goes away:
require_once ( 'path_to_configuration.php' );
require_once ( JPATH_BASE .DS.'defines.php' );

Why does this file have paths hard coded?
Why does it define it's own JPATH_BASE on line 18? Surely the first thing to do is retrieve the real defines that the rest of the site is using? (speculation - I don't know enough about how this component works).

I was going to post a ticket for this but really not sure about giving away super user password (as requested) when I already know what the problem is, I just don't know the best way to fix it.

For the sake of an easy life I could undo the changes to configuration.php and defines.php but a fix to the success.php file would be great.

Many thanks.

I've just submitted a support ticket for this.
Just saying so I don't get duplicate support.

Cheers