Vizio GV42L. Three month ago I bought a Vizio GV42L LCD TV, from first day when turn on the TV,

Question

Three month ago I bought a Vizio GV42L LCD TV, from first day when turn on the TV, the audio is fine but the picture (screen) is black, when I re-start TV all is fine (Audio and video works well). This happen after the TV is off for a long period such as 4 hours.