I added this to my functions.php file
add_filter('init', create_function('$a', 'global $wp_rewrite; $wp_rewrite->author_base = "user"; $wp_rewrite->flush_rules();'));
I have a kind of post that I use for analysis with Metabox. And I want a new type with Metabox. And my problem is that in the second type of post Metabox do not work.