Thanks - that article solved it for me. I didn't have the option to set a featured image from files that weren't in the image library (I usually link to files I store elsewhere). So this helped fix the problem. Thank you!

In the end, I switched to this: http://www.paddsolutions.com/wordpress-theme-neptuniumize/

Just trying to work out how to customise to make the title a little bigger and also to remove one section in the body. My head hurts