Weird error when www prefix used.?!

I’ve heavily modified WP, at least in terms of how a person who can’t program to save his life can modify something.

Anyhow, a blog that I have mirroring content from the main blog is not loading thumbnail images when I load https://www.site.com

If I load https://site.com (no www.), it works perfectly.

When I look at the page source, this is where the problem happens.

https://www.site.com loads this: DOES NOT LOAD THUMBS
background: url(https://tvdl.biz/wp-content/plugins/simple-post-thumbnails/timthumb.php?src=biz/wp-content/thumbnails/86.jpg&w=150&h=&zc=1&ft=png)

https://site.com loads this: LOADS THUMBS

background: url(https://tvdl.biz/wp-content/plugins/simple-post-thumbnails/timthumb.php?src=/wp-content/thumbnails/53.jpg&w=150&h=&zc=1&ft=png

Notice src=biz/wp-content vs src=/wp-content

Any idea how that happened?

Here is the PHP file.

<div class="videoitem">
	<div class="ratings">
    	<?php if(function_exists('the_ratings')) { the_ratings(); } ?>
    </div>

    <div class="thumbnail">
    	<a href="<?php the_permalink() ?>" title="<?php the_title() ?>"><img style="background: url(<?php echo get_thumbnail($post->ID); ?>)" class="thumb" src="<?php bloginfo('template_url'); ?>/images/zoom.png" alt="<?php the_title() ?>" /></a>
    </div>

    <h2 class="itemtitle"><a href="<?php the_permalink() ?>" title="<?php the_title() ?>"><?php the_title() ?></a></h2>
    <p class="itemdesc"><?php the_content_rss('', FALSE, '', 8); ?></p>
    <small class="gallerydate"><?php the_time('F j, Y'); ?></small>
</div>

So how can src="<?php bloginfo('template_url'); be loading differently if it has the www prefix?

I’m pretty well at a loss on this one.

This is the only place it happens. (I have not tried the admin panel on the mirror site, it does not need one.)