salexch

// Constructor / initialize plugin
    function Youtube_shortcode()
    {
        // Load our shortcode only on the frontend
        if ( !is_admin() || FALSE !== strpos($_SERVER['SCRIPT_NAME'], 'wp-admin'))
        {
            // Is it a mobile phone?
            $this->detect_mobile();
            // Guess once host language (used for Youtube's old embed code = Flash only)
            $this->get_hl();
            // do_shortcode() is registered as a default filter on 'the_content' with a priority of 11.
            // To make videos appear on post excerpts follow this guide: https://bloggingsquared.com/blogging-tips/make-shortcodes-work-in-all-wordpress-post-excerpts/
            add_shortcode('youtube_sc', array($this, 'output_html'));
            add_action('wp_enqueue_scripts', array($this, 'output_css'));
        }
        // Allow the button to appear on any rich text editor (i.e. text editor in a widget)

		add_action('admin_init', array($this, 'setup_tinymce_button'));
    }

try this pathch:
in this file
/wp-content/plugins/wpec-related-products/wpec-related-product.php

replace:

function on_wpec_related(){
    global $post;

with:

function mopu_on_wpec_related(){
    global $post, $wpsc_query_vars, $wpsc_variations, $wpsc_custom_meta;

replace:

while($related_product->have_posts()) : $related_product->the_post();

            ?>
<li>
	<div class="prodbox <?php  echo $wp_query->current_post ; ?> product-<?php echo wpsc_the_product_id();?>">
						<div class="prodimg"><a href="<?php echo wpsc_the_product_permalink(); ?>"><img  src="<?php echo wpsc_the_product_thumbnail(); ?>" alt="" title="" /></a></div>
						<div class="prodname"><a href="<?php echo wpsc_the_product_permalink(); ?>"><?php echo wpsc_the_product_title(); ?></a>
						<?php if (wpsc_have_variation_groups()===false) { ?><div class="prodprice"><?php echo wpsc_the_product_price(); ?></div><? }?>
						</div>
					</div>
</li>

<?php
                endwhile;

with:

while($related_product->have_posts()) : $related_product->the_post();
						$wpsc_custom_meta = new wpsc_custom_meta( get_the_ID() );
						$wpsc_variations = new wpsc_variations( get_the_ID() );				

            ?>
			<li>
				<div class="prodbox <?php  echo $wp_query->current_post ; ?> product-<?php echo wpsc_the_product_id();?>">
					<div class="prodimg">
						<a href="<?php echo wpsc_the_product_permalink(); ?>"><img  src="<?php echo wpsc_the_product_thumbnail(); ?>" alt="" title="" /></a>
					</div>
					<div class="prodname">
						<a href="<?php echo wpsc_the_product_permalink(); ?>"><?php echo wpsc_the_product_title();
						?></a>

						<div class="prodprice">
							<?php if(wpsc_product_on_special()) {
							?>
							<span class="salestrike"> <?php }
								echo wpsc_product_normal_price();
							?></span>
						</div>
						<?php if(wpsc_product_on_special()) :
						?><div class="prodpricesale"><span class="salered">?<?php echo wpsc_the_product_price(); ?></span></div><?php endif;
						?>
					</div>
				</div>
			</li>

			<?php
                endwhile;