previous and next link the same for one post only

I have a post on a website its previous and next link display the same post despite other posts being there
any help fixing this would be great.

the problem is here

<div id="primary" class="row-fluid">
		<div id="span12" role="main">

			<?php while ( have_posts() ) : the_post(); ?>

				<?php get_template_part( 'content', 'gallery'); ?>
				<div class="row">

				<div class="span12 text-center">
				<nav class="nav-single">
					<h3 class="assistive-text"><?php // _e( 'Post navigation', 'twentytwelve' ); ?></h3>
					<span class="nav-previous"><?php previous_post_link( '%link', '<span class="meta-nav">' . _x( '←', 'Previous post link', 'twentytwelve' ) . '</span> %title' ); ?></span>
					<span class="nav-next"><?php next_post_link( '%link', '%title <span class="meta-nav">' . _x( '→', 'Next post link', 'twentytwelve' ) . '</span>' ); ?></span>
				</nav>
				<!-- .nav-single -->
				</div>
				</div

				<?php comments_template( '', true ); ?>

			<?php endwhile; // end of the loop. ?>

		</div><!-- #content -->
	</div><!-- #primary -->