Fatal error, site breaking

I just updated (with WP 3.8 and PHP 5.4) and I received the following fatal error:

Warning: require_once(/home/worlds33/public_html/wp-content/plugins/yet-another-related-posts-plugin/class-core.php): failed to open stream: No such file or directory in /home/worlds33/public_html/wp-content/plugins/yet-another-related-posts-plugin/yarpp.php on line 18

Fatal error: require_once(): Failed opening required ‘/home/worlds33/public_html/wp-content/plugins/yet-another-related-posts-plugin/class-core.php’ (include_path=’.:/usr/lib/php:/usr/local/lib/php’) in /home/worlds33/public_html/wp-content/plugins/yet-another-related-posts-plugin/yarpp.php on line 18

On the posts page I’m getting this error:

http://www.worldsfactory.net/2013/12/19/paul-rudd-joins-ant-man

Fatal error: Call to undefined function yarpp_related() in /home/worlds33/public_html/wp-content/themes/worldsfactory/content.php on line 79

Can you please help? Thanks in advance.

http://wordpress.org/plugins/yet-another-related-posts-plugin/