I am also having this same backlight issue. My piece of Crapple is not even two years old. So first off, let be direct an EPIC FAIL towards Apple for making such a pretty, delicate machine that is about as durable as I hadn't bought a inverter, but after reading through some posts, I thought it seemed simple enough to remove the hinge cover and simply check the connections.
If you are considering the method described in this post (accessing the inverter through the hinge cover), think twice. I am a savvy computer tech (I've been building and servicing machines since I was 16). Perhaps my hinge doesn't move as much as those of others who have attempted this technique, but after 30 minutes of frustration, I never did manage to remove the hinge cover and access the inverter. But what I did manage to do was scratch the piss out of the front and back of the cover and unseat the back slots in such a way that I can't properly reseat it. One of the slot arms on the back also snapped.
I don't recommend this method. But what I do recommend is that Apple make a better product in the future.