What version of the theme are you running? Where/when is this happening?
I am running version 0.1 and this appears on the blogroll page. I am using the sample test data, and this happens where the “Post Format Test: Image (Attached)” post should be. Kills the rest of the page from loading.
This also happens on the single post version of this post.
Also affects “Post Format Test: Image (Linked)”
I’m running the same version of 2013 on 3.6-beta1-24067 (haven’t updated WP3.6 today yet) and I’m not seeing the same problems. Both the “Post Format Test: Image (Attached)” and “Post Format Test: Image (Linked)” are loading fine for me – in archive and single post pages.
Maybe try downloading a fresh copy of 2013?