next_post_link / previous_post_link not working with WP_Query

next_post_link & previous_post_link work off the global $wp_query. You could simply overwrite the main query with $wp_query =& $query, or replace your custom query with the standard ‘global’ functions.

<?php query_posts( array( "post_type" => "page", "page_id" => $post->ID ) ) ?>
<?php if ( have_posts() ) : ?>

    <?php while ( have_posts() ) : the_post() ?>
        <!-- do stuff -->
    <?php endwhile ?>

    <div id="footer_nav_container">
        <div class="left"><?php previous_post_link(); ?></div>
        <div class="right"><?php next_post_link(); ?></div>
    </div>

<?php else : ?>

    <!-- do other stuff here -->

<?php endif ?>