Hi Steve,
Well, I've just deleted the three remaining (Mevio) ones in one user account, but I tried your tip anyway as there are still several on my other user account, which has a separate iTunes library. However, For some reason (which I can't yet work out) I cannot change the permissions on the parent file (Windows) or, as a result, on the files within it. So I cannot change the hosts file...
Regarding your previous suggestion about reading the opml file; I assume that your idea was that I could spot the offending URLs. However, I have already identified them all, by attempting to subscribe to each one in turn. The ones causing the Mevio pop-up will bring up the password pop-up when I subscribe. Checking the URLs confirms that they are either Mevio, or Podshow which I think owned Mevio. (Interestingly (perhaps), the Podsafe Music Network is still apparently live (under a slightly different name) and lists its owner as Mevio.)
My answer has been to delete the offending Podcast URL. This does not delete the folder, so if I want to keep the old episodes, with a bit of juggling, I can put them into the Music Library instead.
I also have to revise my comment above (post of June 28th, 5:00pm) about iTunes and whether it deleted Podcasts with this update.
By the way, iTunes did not delete all Podcasts during (or as a consequence of) the update, despite the numerous posts on the subject. After the update, the first access to the Podcasts Library was met with a welcome greeting in place of the expected Podcasts list. The nature of the greeting did make it look as though everything had been deleted. But once the continue button was clicked, the stored Podcasts appeared in a list, as usual.
In fact, several episodes of various Podcast programmes have been removed from my iTunes Library, but are still located in the folder. For example, one Podcast I am currently subscribed to has 87 episodes in the folder, but only three in my Library. All 87 should be listed in my Library, as they were prior to the 11.2 update!
If you are interested, I contributed to this thread: (Why does iTunes constantly ask me for my password when iTunes starts up?) about this subject in order to offer advice (and more detailed information than in this thread) to the OP who is seeing the Podcasts pop-up. He mentions Podcasts in the text. Unfortunately, the specialist who responded has missed the point and has directed the OP to the article iTunes repeatedly prompts to authorize computer to play iTunes Store purchases. I've made it clear in that thread where I think the problem lies, and that it will be a while (if ever) before it is corrected. This is now the second major bodge up by Apple regarding Podcasts, and the first one (the iOS Podcast App) has not yet been recognised and fixed, so I'm not optimistic about this one either.
I'm waiting to get my wrist slapped again as a consequence of that post, and possibly even this one too. (I don't think I'll ever make it to the lounge! )
Phil