Today I noticed that although in Firefox I could see the latest episode (#150) of The JavaPosse iTunes did not notice it, even when I called the "Update Podcast" menu. It still insisted on episode 149 to be the most recent one.
I reloaded the Feedburner feed with F5 and Strg-F5 to no avail. I suspected our company proxy to somehow misbehave and launched Internet Explorer to check what I would get there. Usually I do not use IE, so I could be quite sure to have it request the feed through the proxy and not serve it from its own cache.
To my surprise I immediately got the right, current feed displayed, including Episode #150.
Once I had seen this in Internet Explorer I tried "Update Podcast" in iTunes again and this time it started to download the episode it had not seen before.
I have not bothered to look through the iTunes documentation, so maybe I am writing about something completely normal here, however for me it is definitely counter-intuitive and took me 10 minutes to figure out by trial and error...