Trouble with Creating Custom Menus

[oicurmt3]

This is my site:
http://sandgroper.net/demo

This is the error:

Warning:  call_user_func_array() [function.call-user-func-array]: First argument is expected to be a valid callback, 'register_my_menus' was given in /home/ozscrib1/public_html/sandgroper.net/demo/wp-includes/plugin.php on line 395

This is what I added to my functions.php

// Add Custom Menus
add_action( 'init', 'register_my_menus' );

function register_my_menus() {
    register_nav_menus(
        array(
            'header-top' => __( 'Header Top' ),
            'header-bottom' => __( 'Header Bottom' ),
            'sidebar1' => __( 'Sidebar First' )
        )
    );
}

This is how I've changed (in bold) my header.php

    <div class="headerright">
        <ul id="topnav">
            <?php if (is_home()) { ?>
                <li class="current_page_item"><a href="<?php echo get_option('home'); ?>"><?php _e("Home", 'studiopress'); ?></a></li>
            <?php } else { ?>
                <li><a href="<?php echo get_option('home'); ?>"><?php _e("Home", 'studiopress'); ?></a></li>
            <?php } ?>    
            <?php wp_nav_menu(  array( 'theme_location' => 'header-top' ));  ?> 
        </ul>
    </div>

and

    <div id="navbar">
        <ul id="nav">
            <?php wp_nav_menu(  array( 'theme_location' => 'header-bottom' ));  ?> 
        </ul>
    </div>

This is how my menu backend looks



Any help greatly appreciated

Cheers Pete