Q: playback failed error itunes u

"Error - Playback failed".   I get this error on my iPhone 4s  in iTunes u. The phone software is up to date and I have deleted and reinstalled the iTunes app. The courses are listed on my phone, but they will not playback.  I have connectivity to the Internet and can reach the Apple Store.  These same courses will play back on my old iPod.

I have read the discussions, but there seems to be no answer.