Screen Problem????

I have a Blackbook that is about a year old. Today, when I was about to turn it on, I noticed that about half the screen has a "foggy" or "hazy" look to it - you can't really tell when the computer is on, but when it's off there's a large area that's affected. Does anyone have any idea what this is? I only clean the screen with a damp microfiber cloth - no chemicals - and when I wiped it last Sunday I frankly did not notice any haziness (though maybe I wasn't paying attention). If it doesn't go away, would something like this be covered by Applecare? (Even if it doesn't affect the computer when it is turned on I am anal about these kinds of things. Plus I'm worried - and I've never had to deal with Apple support before.)

 

Could this be humidity under the screen? I just don't know how it got there.