Will it play ANY videos? For example, try the movie trailers associated with movies you might rent through iTunes. Will it play them?
If so, I would assume that your .mov files are encoded beyond the specs of what the

TV1 can handle. If you are familiar with Handbrake, take one of those .mov files and run it through handbrake using the Apple TV (not AppleTV 2 or AppleTV 3) preset. Append the name TEST or something to the end so you can easily recognize it vs. the original in the Apple TV menu. Then try to play it.
If it plays fine, you have files encoded beyond the

TV1 specs. If so, you could run them all through Handbrake with that same setting to adapt them for playback. Or you could buy a newer

TV model and see if it can play back the files "as is".
Alternatively, does the freeze resume? For example, if you wait when one of these freezes, will it resume after a while, maybe play a bit more, then freeze again? If so, that could be network issues. To rule that out,
sync one of the problematic files to the

TV so that it is fully on board and not trying to stream from your computer. If it plays fine off the

TV's hard drive, then I would do some experiments with your network. For example, trying to stream via wifi? Try wired and see if it plays smoothly.