I just had to do a hard reboot on my PowerMac because the OS X Energy Saver locked me out again. I logged in as usual and Folding@home started. Suddenly, the hard disk spun down and wouldn't restart. I tried clicking on the Dock icons but none of the applications would open. Then the video signal from the ATI card was disabled and the monitor went dark. After a minute of pressing keys and clicking the mouse, the system just went to Sleep. I pressed the flashing power button on the Mac and the system started to come up again, but the video signal was still disabled. When I tried to press the button again, it didn't work, and the system kept running with no monitor signal. I had to hold the power button for 5 seconds to power off the system. Why is OS X doing this? Does the PowerMac want me to install Linux?