good day- My powerbook now refuses to turn on after going to sleep. I can hear the machine running, however, the screen is completely black. Even when i hold the ctrl, apple, power button the machine wont restart. I physically have to take out the battery to turn it off and on to restart. The machine works fine as long as i dont put it to sleep. I have repaired disk permissions, with no change. Any idea of the problem whether it would be hardware or software? thanks.