Only some post thumbnails show up in my Category Pages

Hello, I am running WordPress 3.4.1 with “On Demand” theme. It all worked fine until yesterday when some post thumbnails disappeared from all my Category Page listings. It is weird because in some category pages just a few thumbnails appear and in some others none of them at all… But I know they are there, they are just not visible. The tag pages work fine so I don’t know what is going on in my category template? I hope you can help me.

Sample:
https://ilovedolls.net/index.php/category/webcam/

The code I have in my category.php file is the following:

<?php get_header(); ?>

<div id="content">
	<div id="content-inside">
		<div id="post-container">
			<div id="posts">
				<p class="gallery-description"><?php echo of_get_option('category_gallery_description'); ?> <?php single_cat_title(''); ?></p>

				<?php if (have_posts()) : while (have_posts()) : the_post(); ?>
					<?php
						$blog_cat = of_get_option('blog_category');
						if (in_category($blog_cat)) :
					?>

					<?php get_template_part( 'loop', 'gallery' ); ?>
					<?php endif; ?>
				<?php endwhile; else : ?>
					<?php get_template_part( 'loop', 'nothing' ); ?>
				<?php endif; ?> 

			</div> <!-- posts -->

			<?php get_sidebar(); ?>
		</div> <!-- post-container -->
	</div> <!-- content-inside -->
</div> <!-- content -->

<?php get_footer(); ?>