Functions.php not recognizing add_meta_box

None that I know of. All I can suggest is that you try this using the Twentyten theme with all plugins deactivated in case something else is causing a problem.

I’m having the same problem, even with all plugins turned off. Code is below:

add_action('init', 'wpv_custom_post_types');
function wpv_custom_post_types() {
	$labels = array(
	'name' => _x('Cards', 'post type general name'),
	'singular_name' => _x('Card', 'post type singular name'),
	'add_new' => _x('Add New', 'card'),
	'add_new_item' => __('Add New Card'),
	'edit_item' => __('Edit Card'),
	'new_item' => __('New Card'),
	'view_item' => __('View Card'),
	'search_items' => __('Search Cards'),
	'not_found' =>  __('No cards found'),
	'not_found_in_trash' => __('No cards found in Trash'),
	'parent_item_colon' => ''
	);
	$args = array(
	'labels' => $labels,
	'public' => true,
	'publicly_queryable' => false,
	'show_ui' => true,
	'query_var' => true,
	'rewrite' => true,
	'capability_type' => 'post',
	'hierarchical' => false,
	'menu_position' => null,
	'supports' => array('title','editor','author','thumbnail')

	);
	register_post_type('card',$args);
};
add_meta_box('wpv_custom_post_types','Card Options','wpv_custom_post_types','card','side','low');

I have exactly the same problem. Is there no solution so far?
Error message:
Fatal error: Call to undefined function add_meta_box() in /www/htdocs/w00cccaf/wordpress/wp-content/themes/twentyten/functions.php on line 584

I have the exact same problem, too. I just get a blank screen in the admin backend.

I just figured it out. This code works as either a plugin or in your functions.php:

add_action('init', 'jtd_custom_post_types');
function jtd_custom_post_types() {
	$labels = array(
	'name' => _x('Cards', 'post type general name'),
	'singular_name' => _x('Card', 'post type singular name'),
	'add_new' => _x('Add New', 'card'),
	'add_new_item' => __('Add New Card'),
	'edit_item' => __('Edit Card'),
	'new_item' => __('New Card'),
	'view_item' => __('View Card'),
	'search_items' => __('Search Cards'),
	'not_found' =>  __('No cards found'),
	'not_found_in_trash' => __('No cards found in Trash'),
	'parent_item_colon' => ''
	);
	$args = array(
	'labels' => $labels,
	'menu_position' => 30,
	'public' => true,
	'query_var' => true,
	'supports' => array( 'title', 'editor', 'comments', 'revisions', 'author', 'excerpt', 'custom-fields', 'page-attributes', 'thumbnail' ),
	'rewrite' => array( 'slug' => 'provider', 'with_front' => false ),
	'taxonomies' => array( 'post_tag', 'category'),

	);
	register_post_type('card',$args);
};

// This function tells WP to add a new "meta box"
function add_some_box() {
	add_meta_box(
		'ozh', // id of the <div> we'll add
		'My Box', //title
		'add_something_in_the_box', // callback function that will echo the box content
		'card' // where to add the box: on "post", "page", or "link" page
	);
}
// This function echoes the content of our meta box
function add_something_in_the_box() {
	echo "I'm living in a box";
}
// Hook things in, late enough so that add_meta_box() is defined
if (is_admin())
	add_action('admin_menu', 'add_some_box');

Thanks! Worked perfectly.