Hello everyone. Just wanted to post what worked for me. I went through all the official mac steps, nothing worked. Dug deeper and found a "fix it yourself" step by step. It suggested pulling the RAM and then try starting the computer. This worked- The fans came on and the mac steadily beeped (indicating 'no RAM'). Now, one by one I replaced the 4 chips and started it up expecting to find a bad one that was causing my original problem. All 4 are back in and the mac is running just fine!?!? I hope this solution finds you. :0)