I have a Mac Pro connected to two cinema displays(19 inch I think). On November 29, my computer went black after not using it for about a minute. I hit the space bar and the screen was still black, computer unresponsive. I powered off, then restarted and the computer would not reboot. The fan kept blowing until I powered off. Did it again, and again and again. I tried switching keyboards, same problem. I tried a different monitor, same problem. I brought the computer to a Apple store where they cleaned it(vacuumed the inside) and said everything checks out. I'm not sure the problem is fixed. Any ideas on what it might be or what else I can do?