Netflix has released an update for its Windows Phone 8 app to add support for Windows Phone 8 devices running 720x1280 resolution screens. Devices with this resolution previously had a black bar across the top of the screen. Not all phones needed to be updated. For instance, the Nokia Lumia 920 retained the aspect ratio of previous Windows Phone 7 devices. This update adds full support for the aspect ratio supported by Windows Phone 8.
If you're one of the unlucky ones that wasn't supported, you can download the updated app from the Windows store.