Related Post v 2.0.1 plugin by WASABI is the first plugin I installed on my WordPress script for this blog.
The setup script of this plugin failed to activate. So I was forced to setup the database manually as instructed on its readme-first file.
After inserting the code into the theme file, I got an error message like this:
SELECT ID, post_title, post_content,MATCH (post_name, post_content) AGAINST (wordpress skins) AS score FROM wp_posts WHERE MATCH (post_name, post_content) AGAINST (wordpress skins) AND post_date
I thought at first the problem is on my database. But then I found out that there was a tab installed on my WordPress admin window which I failed to update.
Well, after updating the options for this great plugin, everything went fine already.
Thanks to the creator of this.