Hey Martin, thanks for reaching out, I'll gladly help!
I immediately tried to reproduce the problem on several of our blogs, but unfortunately, everything ran smoothly. :/
Are you running any special settings on either of the plugins? If so, which ones? What is the exact problem you are experiencing? Any particular error messages (if so, which ones)?
I also noticed a small message at the end of your blogpost that's quite intriguing to us, especially since it's not included into our plugin. It says: "Activate the Wp-related-posts plugin to see the related post list!"
Here's the link to the screenshot I made: http://cl.ly/image/2R1q0G170v12
Any clue where this message is from?
We'd love to help you out, so any kind of additional information/feedback is greatly appreciated! I'm looking forward to your reply!