I did talk to Apple Support about a month ago, and they walked me through shutting down Home Sharing on my Mac and all devices, and then restarting all hardware, and then restarting Home Sharing on everything.
This got my library to finally load, and I was able to stream the movies to my iPad. But it lasted for less than a day, and now I'm back to where I started, unable to load the library in the Videos app or the Music app.
I don't have to do this with my iPhone (4, OS6) or appleTV, and I certainly don't want to reboot everything in order to stream a movie or music onto my iPad.
Again, Apple, what gives?