On iOS 8.1.1, (iPad Retina and iPad Air 2), I can stream my podcasts but once I download them, they are not playable.
I will get "Episode Unavailable" once the download complete. Other podcasts I've tried seem to work. I'm encoding at 96kbps CBR, 44.1Khz stereo, MP3. I've tried adding the tags such as Podcast, Title, etc. but it still gives that error. iOS 7 seems fine though (tested on iPhone 4S and 5).