Gallery Link From Thumbnail To Fullsize Image

Hello,

I’m trying to have a gallery with thumbnails that link to the full size image in a post, so that when clicked the gallery thumbnail will open a lightbox with the full image. So far, I’ve tried using wp_get_attachment_link() and the_attachment_link(), which I thought should have done the trick. But it only resulted in a “missing attachment” message.

Here is the loop I have so far:

<ul id="portfolio-list">
			<?php query_posts('cat=5&showposts='); ?>
			<?php if ( have_posts() ) : while ( have_posts() ) : the_post(); ?>
				<li class="<?php $category = get_the_category(); echo $category[0]->cat_name; ?> all">
					<a href="<?php the_attachment_link();  ?>">
						<?php the_post_thumbnail(); ?>
						<h3><?php the_title(); ?>.</h3>
						<p><strong>tags:</strong> <?php $category = get_the_category(); echo $category[0]->cat_name; ?></p>
					</a>
				</li>
			<?php endwhile; ?>
			<?php endif; ?>
		</ul><!-- /#portfolio-list -->

Thanks