OK, so I have read most of the start up problems, and mine is different. Whenever I shut down and try to start my computer again, I am not able to get my computer to turn back on. I hit the power button, and hear the computer humming, but not the typical hum-hum that usually occurs. My screen remains black with no activity. After 5 to 10 attempts at this, the computer starts up fine, and I have no problems with it running. I do not have this problem when I use the restart function, say after I download a software update. This problem is driving me nuts as I am afraid I can not shut off my computer! Can anyone help me out, or possibly know why this is occurring?