I've noticed this in the last few posts I've made recently.
I'm using Ubuntu 13.10 with Firefox 30 (including a bunch of addons: NoScript, Session Manager etc.) I'm not blocking any content from this site.
After I press the "Preview" button, the "Preview Post" div shows up with the text "Fetching preview..." in it. But no preview ever shows up.
Anyone else having this problem?
Cheers,
Nap