My HP ProBook 4320s laptop constantly gets black screen. Im normally using it then after a while i get a light black screen, the laptop still runs and it s on but it doesnt really works, i change the setting that when i close the cap the laptop is going to shut down, it worked onece but when i got the black screen i closed the cap nothing happens. And the screen doesnt comes back. I have to close it by holding the power button. Can someone help me?