As I posted in the support forum on wordpress.org earlier, I had some problems after activating the wordpress plugins
Those plugins can be configured to automatically show up without having the need to manually insert template tags in your theme – which is done by “hooking” into The Loop.
The only problem was: if the post was rather short, the texts that were created from the plugins were also shown within the_excerpt() and in the text of pingbacks and trackbacks – meaning that those texts (like e.g. “Add this post to:“, which I use as title for “Social Bookmarks”) were behaving like a real content of a post.
Simply turning off those automatic “hooks” and manually inserting the template tags for each plugin into the theme template after the_content() did the magic!