Hi Jon.
The thread is quite old and recent updates seem to have resulted in my library being available all the time now, there were also a fair number of people reporting the same issue at the time and I haven't seen too many since, although there are a couple of new additions to this thread very recently.
There may have been some mileage in your suggestion though:
My library is on 3 internal green enterprise drives which are software raided (separately from my system drive), being green they spin down independently of system settings. Occasionally I have to wait a second or two to use iTunes on the mac and probably about one in fifty times on the Apple TV 1, after selecting a movie it will give me the message 'no content found', and I have to press menu and select the video again. It's not all that inconvenient and I love the silence when working at my mac.
I'm guessing the time the Apple TV 1 allows to find the movie is maybe a fraction longer than it takes my drives to spin up on average and why on occasions I get the 'no content' message.
Assuming the previous software version running on the Apple TV 2 gave less time to locate the library (slightly different I know but a little similar) than it took the drives to spin up then it could have been the reason for the no library message.
Further assuming more recent software is allowing more time to locate the library, I can't really test your suggestion anymore.