If you are experiencing a breaking-up TV picture or signal interference from an unknown source, consider whether a nearby device, such as an airport radar, could be causing the problem. Use Google or Bing Maps to do a quick search for airports in your area.
Radiating frequencies from airport radars, or in-car radar detectors and jammers, could interfere with your TV signal. Source: How do I set up my Sky+HD Box?
If this is the case, you may need to move your Sky dish to a new location, such as behind a wall, where it can be screened from the source of interference.
Make sure that the new location still allows the dish to have an unobstructed view of the satellite, and that it is not in a place where it could be accidentally moved or obstructed. This oftentimes happens when you are moving home and the signal stops working.