I have had 2 of these. They work fine one minute, then the next they won't turn on and make my tv go blurry. I have no idea why this keeps happening. I had each of them since the big switch to digital. They have enough ventilation room, nothing has fallen or spilled on them, I have no idea what is wrong with them. Have they just gon past their lifetime? Did they come from a bad shipment? Please help me