Attaching multiple custom taxonomies to one CPT?

First off, what WordPress version are you using? Second, here’s a Custom Post Type with 2 Taxonomies. It is a bit lengthy as I am copy / pasting it straight from one of my projects, feel free to view the codex and add or omit things as you see fit.

First I register the post type – following the standards.

/** Create Post Type **/
function CPT_init(){
    // Products CPT 
    register_post_type('product', array(
        'labels'            =>  array(
            'name'          =>      __('Products'),
            'singular_name' =>      __('Product'),
            'all_items'     =>      __('View Products'),
            'add_new'       =>      __('New Product'),
            'add_new_item'  =>      __('New Product'),
            'edit_item'     =>      __('Edit Product'),
            'view_item'     =>      __('View Product'),
            'search_items'  =>      __('Search Products'),
            'no_found'      =>      __('No Products Found'),
            'not_found_in_trash' => __('No Products in Trash')
                                ),
        'public'            =>  true,
        'publicly_queryable'=>  true,
        'show_ui'           =>  true, 
        'query_var'         =>  true,
        'show_in_nav_menus' =>  false,
        'capability_type'   =>  'post',
        'hierarchical'      =>  false,
        'rewrite'           =>  array('with_front' => false),
        'menu_position'     =>  21,
        'supports'          =>  array('title','editor', 'thumbnail'),
        'has_archive'       =>  true
    )); 
}
add_action('init', 'CPT_init');

Next I create the 2 taxonomies for my Custom Post Type – Products

One will be for Product Categories and the other will be for Product Manufacturers.

/** Add Custom Taxonomy **/
function product_category_taxonomy() {
    $labels = array(
        'name'              => __( 'Product Categories' ),
        'singular_name'     => __( 'Product Category' ),
        'search_items'      => __( 'Search Product Categories' ),
        'all_items'         => __( 'All Product Categories' ),
        'parent_item'       => __( 'Parent Product Category' ),
        'parent_item_colon' => __( 'Parent Product Category:' ),
        'edit_item'         => __( 'Edit Product Category' ), 
        'update_item'       => __( 'Update Product Category' ),
        'add_new_item'      => __( 'Add New Product Category' ),
        'new_item_name'     => __( 'New Product Category' ),
        'menu_name'         => __( 'Product Categories' ),
    ); 
    $args = array(
        'labels'            => $labels,
        'public'            =>  true,
        'hierarchical'      =>  true,
        'show_in_nav_menus' =>  false,
        'has_archive'       =>  true
    );
    register_taxonomy( 'protax', 'product', $args ); 

    $labels = array(
        'name'              => __( 'Manufacturers' ),
        'singular_name'     => __( 'Manufacturer' ),
        'search_items'      => __( 'Search Manufacturers' ),
        'all_items'         => __( 'All Manufacturers' ),
        'parent_item'       => __( 'Parent Manufacturer' ),
        'parent_item_colon' => __( 'Parent Manufacturer:' ),
        'edit_item'         => __( 'Edit Manufacturer' ), 
        'update_item'       => __( 'Update Manufacturer' ),
        'add_new_item'      => __( 'Add New Manufacturer' ),
        'new_item_name'     => __( 'New Manufacturer' ),
        'menu_name'         => __( 'Manufacturer' ),
    );
    $args = array(
        'labels'            => $labels,
        'public'            =>  true,
        'hierarchical'      =>  true,
        'show_in_nav_menus' =>  false,
        'has_archive'       =>  true
    );
    register_taxonomy( 'mantax', 'product', $args ); 
}
add_action( 'init', 'product_category_taxonomy');