April 26, 2012 9:58 AM PDT
Without some more detailed information it is hard to diagnose the issue. The Apple TV should play the video at whatever frame rate it is encoded as and other than the 'cinematic' look of 24fps (which is also roughly the frame rate of PAL) there shouldn't be anything blotchy.
It could be the specific download had an encoding issue, or it is a network latency issue.
If you have more info perhaps we can direct the question to someone who could get a better answer for you.