Waited too long to edit my previous post.
I've tried a couple of different ways of making it work better with 1.5 - one was to add
<?php require('wp-blog-header.php'); ?> to the start of the file, which meant that I could then use
<?php get_header(); ?> etc to draw the header & footer & sidebar.
The other thing I tried was using the phpexec plugin to paste the narchives code onto a page - however, the problem that arose with both of these was that it stopped showing all of the posts, & only shows about 10 now.