Check your TV can take that. It may only be 720. I'd go to the control panel settings thing in the dashboard and gradually increase it from 480 until it works.
Also, do you have a HD or component cable? If not, you need one of them. A scart lead can only take 480 if you're lucky (from memory). If you're using the component lead (the one with 6 connectors) ensure you have the correct colours in the correct positions (there should be green, blue, red for picture and also red, white and another- its this other lead you leave out, thats only for when you use it as AV (red, white, yellow)
Old matey boy!, April 2009