Need some quick php help

Hiya

I have been working on a blog with wordpress, and when I click on a certain category it only brings up one post on the category page instead of a list of posts in that category.

I have looked in the admin panel to see if it is as simple as turning it on and off, but I cant seem to find anything.

Anyway this is the code in the category.php template:

<?php get_header(); ?>

<div class="post">
<h2 class="section-header"><?php single_cat_title(); ?></h2>
<div class="entry">
<?php echo category_description(); ?>
</div>
</div>

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

<div class="post">

<h3 class="post-title">
<a href="<?php the_permalink(); ?>" title="<?php the_title(); ?>"><?php the_title(); ?></a>
</h3>

<?php echo get_the_image_link(array('Thumbnail'), 'thumbnail'); ?>

<div class="entry">
<?php the_excerpt(); ?>
</div>
</div>

<?php endwhile; ?>

<?php else: ?>

<p><?php _e('Sorry, no posts matched your criteria.','structure'); ?></p>

<?php endif; ?>

<div class="navigation-links section">
<?php posts_nav_link('',
'<span class="previous">&laquo; '.__('Previous Page','structure').'</span>',
'<span class="next">'.__('Next Page','structure').' &raquo;</span>'
); ?>
</div>

<?php include(TEMPLATEPATH . '/includes/widget-blocks.php'); ?>

<?php get_footer(); ?>


What would I need to change in that code to get the category pages to list more posts from that category instead of just one post.

Any help would be appreciated.

Thanks
Clare