Thank you for your help, though I didn’t use your code but it gave me an idea to use the plugin code into a hook which execute out of the loop now it is working fine the way i want.
It was working fine if I unchecked the Auto inserted post option in Pluggin settings and put the code (<?php wp_related_posts()?>) manually through Genesis Hooks at the end of post but another problem came up.. in the category page the related post is shown after each excerpted post one after another so I undo this steps.
