I like to insert the related posts manually with echo related_posts(); in single.php.
If i do so, I get them twice. Example: http://www.testspiel.de/archives/2012/05/08/deine-freunde/ (in German: "Zum Thema")
I always did it that way, but since - I think - the last version, I have this bug.
Any other manually plugin integration within the single.php works great.
The auto display for yarpp also works.
Thanks in advance!