Where did you get the file? The particular format may be unsupported. Try converting it to a production codec. Highly compressed sources are never a good choice for compositing. I even convert Sony XD Cam or footage from a Canon DSLR to something more friendly. You can use QT any number of programs to convert (transcode) your original to a more friendly codec like Apple ProRez, Black Magic, Motion JPEG, or a ton of others.
Here's some more detail about what Szalam said about the trial version: