That seemed to do it. I had only typed in http://www.trendybingo.com as a feed adress, not including the “/?=feed=rss2”. Thanks!
Thank you so much, that solved it!
Thank you, that sorted it! However, there’s one more little problem, still linked to the length of the excerpt used in the post. If you check the sidebar now, there is a 2 px gap between every thumbnail that has two rows of excerpt, apart from the second thumbnail (which only has one row of text) which is positioned right under the first, without a gap in between.