I've got a custom publish typed known as Uploads on my small Wordpress site which (using v3.1) comes with an index archive only at that url:
Now since this is produced instantly by WordPress with no page as with previous versions of Wordpress I'm not able to produce a sub-page like so:
How do i produce a page and alter it's hyperlink to fake it therefore it looks a young child page of uploads?
This labored for me personally: http://wordpress.org/extend/plugins/custom-permalinks/
Have you try the url edit function, in edit page?