Didn't know where else to post this, so... For the last few weeks, I haven't been able to download any of the video podcasts I'm subscribed to in iTunes. (I'm subscribed to the After Effects and Premiere ones, and just tried with the new DSLR Video one; all of them are SD). The new episode shows up in the iTunes episode list, starts downloading automatically... but never finishes; eventually, after downloading about 50% to 80% of it, it will just stop with a network timeout error.
Other users who have experienced something similar have found that their is generally something in their ISP's firewall settings that is contributing to the issue. You may need to try downloading from a different connection if the problem persists.
Thanks for your answer. Today I tried downloading the RSS feed of the DSLR Video podcast, opening it with a text editor and looking for the URL of the video file in order to download it "by hand", and managed to do so without any problems. I'm using the same computer, same ISP, no changes in any firewall settings.
Then I tried downloading the same file again from iTunes, and it stopped halfway through with an "error -3259". Apple's support document says that it can happen (aside of firewall issues) "if you are using an older version of iTunes", which I am (iTunes 220.127.116.11). If I have time, I'll try installing the latest iTunes and see what happens.