Well according to author of the plugin, it has been solved, as the latest YARPP plugin still shows twice results it is because of calling the function in a improper way for example :
<?php echo related_posts(); ?>
well the solution to problem is simple just remove the
echo from above code so it will become :
<?php related_posts(); ?>
Well your YARPP plugin is fixed.
Don't have YARPP plugin well you can download it from here