Just realized I accidentally posted this to a resolved post.
I just installed this plugin and I'm having the same issue. I get the text for the recent posts, but the Like and Comments are just text links and no images will show. I have tried both Thumbnails and Normal and tried various widths and heights and even taking out the width/height specs altogether. Also there is a blank post at the very top of recent posts that makes no sense because it is also displaying our most recent post just fine.
The widget is on the right side near the bottom.