JVC lcd tv - no picture, sometimes!?

Hi, there is a problem with our JVC LCD tv, the sound is fine, but there is often (but not always) no picture when it is swiched on. It is about 6 years old, and the backlights are fine, and nothing inside looks blown or distorted. It appears to be that the y-spread (vertical) is not functioning properly (if there is such a thing in a flatscreen!) as often a thin bright line will appear across the very top of the screen when there is no picture. Sometimes there will be no picture for 10mins (for example) and then the picture will reappear of its own accord, and sometimes it will appear instantly, or not at all regardless of how long it's left on for. Often the screen is bright grey when switched on, fading to black. The problem seems intermittent/random at the moment, which is the most puzzling thing! If you have any idea what might be on its way out any help would be most appreciated! Cheers, Keri