I cant get pagination on my custom post page to work with the following code:

<?php get_header(); ?>
			<section id="content">
				<aside class="left-col">
					<?php dynamic_sidebar( 'linker-sidebar' ); ?>
				</aside>
				<article class="right-col">
					<section id="slider">
					<?php nivo_slider( "home-slider" ); ?>
					</section>
					<ul class="productthumbnails">
						<?php
						$paged = (get_query_var('paged')) ? get_query_var('paged') : 1;
						$mijnProducten = new WP_Query( array(
						'post_type' => 'producten',
						'posts_per_page' => 3,
						'orderby'=> 'menu_order',
						'paged'=>$paged
						) );
						while( $mijnProducten->have_posts() ) : $mijnProducten->the_post();
						?>
							<li><?php the_post_thumbnail( 'postpage'); ?> <h2><?php the_title(); ?></h2> </li>
						<?php
						endwhile; ?>
						<div class="alignleft"><?php previous_posts_link('&laquo; Previous') ?></div>
						<div class="alignright"><?php next_posts_link('More &raquo;') ?></div>
					</ul>
				</article>
			</section>
		</div>
		<?php get_footer(); ?>

I was wondering how i can fix it and what I am doing wrong.