Problem with post page navigation

Hey all..

On this page here I’ve restricted WP to only showing the latest 3 posts from that category. The problem is since I have more than 3 posts, the page navigation isn’t showing up! Even when I tried to use Lester Chen’s navigation plug in, its not showing the other page….

Here’s the WordPress code for that section

<?php $my_query = new WP_Query('cat=4');
  while ($my_query->have_posts()) : $my_query->the_post();
  $do_not_duplicate = $post->ID;?>
  <div class="titles">
  <h2><a href="<?php the_permalink() ?>" rel="bookmark"><?php the_title(); ?></a><br />
<?php the_time('m.d.Y'); ?></h2>
  </div>
		<?php the_content(__('(more...)')); ?>
  <?php endwhile; ?>
 <?php next_posts_link('&laquo; Previous Entries') ?>
 <?php previous_posts_link('Next Entries &raquo;') ?>
  <?php if(function_exists('wp_pagenavi')) { wp_pagenavi(); } ?>
    </div>
    <?php get_footer(); ?>

Thanks if anyone could help me out!

Eric Huang