Hi b noir,
I'm trying to watch video podcast on iTunes U on my computer, instead of my phone. When I click to watch the video once downloaded (which works), either nothing happen or the video screen launches and starts to play for the duration of the podcast, but with a black screen and no sound. the behavior depends on the file. The file which plays a black video will always play a black video, the one that doesn't play at all will never do anything.
Thanks for your help.
Just in case (even though you're not getting the standard symptoms), try relaunching iTunes in 32-bit mode prior to attempting to watch the videos as per the instructions in the following document:
Any better luck with getting them to play?