Double Pictures

When I set a featured image for a new product, I get two photos displaying. One is the dominant and one is a thumbnail directly below it. I tried searching through my theme's function.php and commenting out it's function to display post's thumbnails but had no success. When I ventured to the marketpress/marketpress-includes/template-functions.php and commented out

$image = get_the_post_thumbnail($post_id, $size, array ('class' => 'alignleft mp_product_image_'.$context, 'title' => $title));

.. part of my problem was solved. The thumbnail was removed from the products page, however I also lost the thumbnail on the product list. Is there anyway of fixing the double image problem without losing my product list thumbnail?

Many thanks in advanced.