Every time my 2007 MacBook wakes from sleep, the screen stays black. Even though it's almost impossible to see, the screen is active, which lets me save open documents before shutting down. If I try to adjust the contrast, I can faintly see the contrast bars changing. But the screen itself stays black, same as if I had turned the brightness to 0/16. I've reset the PRAM and the NVRAM multiple times. Each time, it briefly resolves the issue. But once I finish this post, if I close the Macbook or it goes to sleep, the screen will stay black next time it wakes up. Any ideas? Thanks!