I have a mid 2011 27" iMac. Basically I was using my system and suddenly a big spot near the center of the screen started making it hard to see, and now it makes everything within that area, very blurry. What can I do? Is there a way to fix this? Is it the humidity? I hadn't used this system for about 2 1/2 months. Should I employ my Applecare? Thanks!