Hmm, I just noticed that my Zune software is refusing to download this episode! (as a true J. Allard follower I still do all of my podcast listening on my 120GB Zune)
Upon closer inspection, the most recent episodes of Designer Notes and Idle Weekend refuse to download as well. My Waypoint and Giant Bomb podcasts are still downloading fine, so it seems to be limited to Idle Thumbs hosted podcasts.
As an experiment I tried subscribing to the Idle Book Club and all episodes refused to download. Subscribing to a random NPR podcast seemed to work fine.
Have there been any changes to how podcasts are hosted/delivered recently that might cause issues with Zune software?