campo personalizado en wordpress no guarda datos

[ArturoGallegos]

yo siempre uso esta estructura y nunca me ha fallado

Código PHP:

<?php
add_action('admin_init', 'register_TypePost_fields');
add_action('save_post', 'update_TypePost_fields');
function register_TypePost_fields(){
    add_meta_box('ID_fields', 'title fields', 'add_TypePost_fields', 'TypePost', 'normal', 'low');
}
function add_TypePost_fields(){
    global $post;
    $custom = get_post_custom($post->ID);
    if(isset($custom['NameField'])){$NameField = $custom['NameField'][0];}
    else{$NameField = '';}     
?>
<div class="custom_fields">
    <label>NameField:</label><br /><input name='NameField' value='<? echo $NameField; ?>' style="width: 100%;" />
</div>
<?php
}
function update_TypePost_fields(){
    global $post;
    if(isset($_POST['NameField'])){update_post_meta($post->ID, 'NameField', $_POST['NameField']);}
}
?>