Restarting is quick and easy (menu and down for 6 secs on TV, or unplug power).
Not normal but not unheard of for there to be times when access to the store is problematic - rare in my experience.
Playing from the cloud is all very well, but less robust than playing from an itunes library on a local computer. If you download the TVShows to there they would be available without using internet bandwidth but the computer has to be on with iTunes running.
Thanks for the insight - it seemed to magically fix itself before I had a chance to try a restart. In the meantime, I went through and downloaded my purchases to my Mac. It was high drama when my preschooler couldn't watch her show. Flakiness is the main reason we ditched cable television for iTunes, so I hope this isn't a usual occurance.