The files that appear to have changed in WordPress version 1.5.1.2 from 1.5.1.1 are:
\wp-content\themes\default\header.php \wp-includes\functions.php \wp-includes\template-functions-category.php \wp-includes\template-functions-general.php \wp-includes\version.php
Please note that the above is not an official WordPress list. It was made using the win32 program WinMerge, from zip downloads of WordPress versions that I have saved.
