I have been struggling to make my sidebar show in single posts, am using a modified version of the Kubrick theme. Here is the code from single.php
<?php get_header(); ?>
<div id="content" class="narrowcolumn">
<?php if (have_posts()) : while (have_posts()) : the_post(); ?>
<div class="post" id="post-<?php the_ID(); ?>">
<h2><a href="<?php echo get_permalink() ?>" rel="bookmark" title="<?php _e('Permanent Link:'); ?> <?php the_title(); ?>"><?php the_title(); ?></a></h2>
<div class="entrytext">
<?php the_content('<p class="serif">'.__('Read the rest of this entry »').'</p>'); ?>
<?php if (function_exists('gengo_link_pages')) : ?>
<?php gengo_link_pages('<p><strong>'.__('Pages:').'</strong> ', '</p>', 'number'); ?>
<?php else : ?>
<?php link_pages('<p><strong>'.__('Pages:').'</strong> ', '</p>', 'number'); ?>
<?php endif; ?>
<p class="postmetadata alt">
<small>
<?php printf(__('Filed under %3$s. Track the latest entries via our <a href="%4$s" rel="nofollow">RSS 2.0</a> feed.'), get_the_time(__('l, F jS, Y')), get_the_time(__('g:i a')), get_the_category_list(', '), get_bloginfo_rss('comments_rss2_url')); ?>
<?php if (('open' == $post-> comment_status) && ('open' == $post->ping_status)) {
// Both Comments and Pings are open
printf(__('You can <a href="#respond">leave a response</a>, or <a href="%1$s">trackback</a> from your own site. '), trackback_url(false));
?>
<?php } elseif (!('open' == $post-> comment_status) && ('open' == $post->ping_status)) {
// Only Pings are Open
printf(__('Responses are currently closed, but you can <a href="%1$s">trackback</a> from your own site.'), trackback_url(false));
?>
<?php } elseif (('open' == $post-> comment_status) && !('open' == $post->ping_status)) {
// Comments are open, Pings are not
_e('You can skip to the end and leave a response. Pinging is currently not allowed.');
?>
<?php } elseif (!('open' == $post-> comment_status) && !('open' == $post->ping_status)) {
// Neither Comments, nor Pings are open
_e('');
?>
<?php } edit_post_link(__('Edit this entry.'),'',''); ?>
</small>
</p>
</div>
</div>
<?php comments_template(); ?>
<?php endwhile; else: ?>
<p><?php _e('Sorry, no posts matched your criteria.'); ?></p>
<?php endif; ?>
</div>
<?php get_sidebar(); ?>
<?php get_footer(); ?>