If you are getting a white screen, try restarting the AppleTV. Hold the minus "-" button and the menu button until the LED on the front of the system turns amber, then release. Your screen will flash a few times and then it will ask you to select the language and present you with an option to Restart, choose that option. The screen will flash a few times more and then the system will start-up. Try the movie once it is restarted.
This will not erase any settings, it is just the equivalent of restarting a computer.
The problem with getting a white screen happens to me about once every other week. It's either because of the HDMI switch I use, or that in combination with using a Dell monitor. Something happens with video content that stops it from working. The restart fixes it every time.