[Plugin: Best Related Posts] Thumbnails not working

As you can see on this post (bottom of the page). The text is showing up but no images. I did have one article that showed an image briefly, then disappeared when I reloaded the page. I have images uploaded to WP for all my posts so not sure why it isn’t working. How can I trouble shoot this?
Thanks.

http://wordpress.org/extend/plugins/best-related-posts/