After briefly scanning the eleven defects fixed in 1.5.2 (an interim release before WordPress 1.6) I identified the changed files.

They are:

xmlrpc.php
comment-functions.php
wp-admin/post.php
pluggable-functions.php
registration-functions.php
wp-admin/categories.php
wp-commentsrss2.php
wp-includes/template-functions-category.php
edit-page-form.php

I am shortly planning to provide a patch update from 1.5.1.3 to 1.5.2. Hang on.