Any reasons and solution to this problem?
Urgent response would be appreciated.
sbiddle: How do you have your decoder hooked up to your TV? To get the best picture quality you need to be using a component cable bwteeen the Sky decoder and TV. If you aren't using component then you won't be getting the best picture quality.
Reading your original post again makes me thing that you're just using the RF outout from the Sky decoder rather than an AV input. If so this will result in the worst possible picture output from the decoder.
Sky's picture quality however is only average, especially compared to the Freeview|HD channels.