My Z works again, though for how long, I don't know. It seemed as if the battery was drained, probably by leaving Opie player on. Is your battery dead? For a while, I wasn't even getting LED lights, then after frequent resetting, the battery light came on and stayed on for a long time. I would check the battery or get a replacement. It seems as if when the battery is drained, it wont turn on, even if its plugged in.
hope my melodrama helps.