Parse error endwhile

Bonjour,
j'ai un problème sur un template de theme wordpress :
parse error sur ligne 62 qui correspond à :
<?php endwhile; ?>
Voici le code complet (depuis le début du while)
<?php if (have_posts()) : ?>
<?php while (have_posts()) : the_post(); ?>
<?php
$thumbnail = wp_get_attachment_image_src(get_post_thumbnail_id(), 'large');
?>
<div class="poster">
<div class="leftside">
<div class="inline-byline">
<a href="<?php the_permalink(); ?>" title="<?php the_title(); ?>" class="date-num"><?php the_time('j') ?></a>
<a href="<?php the_permalink(); ?>" title="<?php the_title(); ?>" class="date-month"><?php the_time('M') ?></a>
<span>Autor:</span> <span class="inline-byline-author"><?php the_author_posts_link(); ?></span>
<span class="comment"><?php comments_popup_link('0', '1', '%'); ?></span>
</div>
</div>

<div class="post postcontent">
<?
// checks if thumbnails are disabled
if ($xs_disable_thumbnails_archieve == "true") { ?>
<? } else { ?>
<?php
if ( has_post_thumbnail() ) {
// the current post has a thumbnail
?>
<div class="thumbnail-wrap">
<a href="<?php the_permalink(); ?>" title="<?php the_title(); ?>"><img src="<?php echo $thumbnail[0]; ?>" height="270" width="560" alt="<?php the_title(); ?>" class="thumbnail" /></a>
</div><!-- /thumbnail-wrap -->
<? } else {
// the current post lacks a thumbnail
?>
<? } ?>
<? } ?>
<h2 class="entry-title"><a href="<?php the_permalink(); ?>" title="<?php the_title(); ?>"><?php the_title(); ?></a></h2>
<?
// checks if the byline is disabled
if ($xs_disable_inline_byline == "true") { ?>
<?
// if not show byline
} else { ?>

<? } ?>
<?php the_excerpt(); ?>

</div><!-- /post postcontent -->
<div class="clear"></div>
</div>

<?php endwhile; ?>
<?php endif; ?>