If you change the name of custom post types, all the posts published with the previous name will lead to 404 error. Run this small SQL query to rename your post types and taxonomies without any problems.
[php]UPDATE `wp_posts` SET `post_type` = ‘<new post type name>’ WHERE `post_type` = ‘<old post type name>’;[/php]
[php]UPDATE `wp_term_taxonomy` SET `taxonomy` = ‘<new taxonomy name>’ WHERE `taxonomy` = ‘<old taxonomy name>’;[/php]