sounds like the LCD backlight isn't working. you may want to check these connections on the motherboard and on the LCD panel for the LED back light. Also, you may want to connect your old display to see if the problem is reproducible. Tim
If it is cracked along the edge near where your palms rest you be able to get it replaced under warranty. Several others have had the same issue. Try to visit an Apple Store and see if tehy'll replace it for free.