loyan, this could be a bad LCD (broken backlight) as well as a signal issue. Disassemble your nook and take a look at the connector, make sure it is properly seated. If it is and the components do look okay, I would start with a replacement LCD. You are looking for a LD070WS2 (SL)(02) LCD, available at places like ebay for around $70. Here is the teardown that will give you an idea of what is involved when working on a Nook.