It's not going to be dead pixels. They don't occur in lines, sounds like a general screen fault. How long have you had the it? Warranty return it if you've had it for less than a year, if you can't because you've had it longer then I'd try taking it to an Apple store. They are normally quite good with stuff like this even if a device is out of warranty.
Well, I managed to fix it, by applying massive amounts of pressure onto the screen, creating that watery affect, and what do you know - the black line started to fade.
Turned it off for an hour, upon resuming it, it has disappeared all together.
Thanks.