Fatal Error When Viewing Listings

Okay, so I have installed the directory plugin with no other plugin and version 3.3.1 of wordpress. I have gone through the settings and I have a couple of errors.

1. The signup page is not showing--when I click to view the sign up page, I get taken to the home page.

2. When I view the listings with the shortcode I get this error: Fatal error: Call to undefined function the_post_thumbnail() in /home/atlante/public_html/ins/wp-content/plugins/directory/core/core.php on line 977. What is that? I don't have post thumbnails when adding a new listing.

Please help! Site: http://www.drummerboyhosting.com/ins

Thanks!