While the iTunes Store (iTS) still shows only up to #491, I was able to update a newly added podcast, following this procedure:
Open up iTunes, go to File -> Subscribe to Podcast, enter
http://www.eevblog.com/feed/ in the URL textbox, click ok. This creates a new entry in the podcast list called "EEVblog - The Electronics Engineering Video" [ the old one had "Podcast feed" added to the name.
So I have two Podcast feeds now, the old one up to episode #491 and the new one (#463 - #501).
This new podcast feed gets updated, so this means the feed.rss file is correct. As I circumvent the iTunes server, the error must be within the iTS. It looks that it does not update the feed anymore, due to a blocking status on the iTS side. Maybe you could contact Apple iTunes support to look into it, otherwise the EEVBlog probably vanishes from the iTunes directory...
I also looked at your feed.rss, I couldn't find any issue other than it's not nicely formatted
.
Hope this helps a bit to everyone.
Thomas