how can i fix my sky+box is not showing a picture on my tv?

my sky tv was working ok yesterday afternoon but by nite time it had gone off the picture .I have tried all the leads i.e scart ,ariel .i have un screwed the leads to the sky box and i have re-booted the sky box.ALL I GET IS A GREEN LITE ON THE BOX AND WHEN I PRESS ON THE REMOTE THE LITES FLASH ON THE BOX AS NORMAL BUT STILL NO PICTURE COMING THROUGH