Samsung SP-50L7H No Picture But Sound

[discodaz]

my Samsung SP-50L7H has been acting up recently, its totally random (might happen 3 or 4 times a night might go for days without doing it) the screen flickers (black & white vertical stripes) then a few minutes later the screen goes blank you can hear the sound and see the light escaping from the back so the lamp is still on! any ideas??