All I can say is, "oh no!" I upgraded my 2009 Mac Pro firmware to 5,1 then upgrade the CPUs to two 6-core processors, upgraded to 1333 memory, turned it on, works...life was good!! I migrated my Macbook Pro user files over to the hot rodded mac pro. Smooth sailing. Now I wanted to see how fast it would render a file in blender..so loaded up a file and rendered...hmmm pretty fast. Lets see how much faster than my Macbook pro i7. I started blender on the MBP and loaded the same file... then simultaneously hit "render image" on both machines. After 10 seconds the mac pro froze. "huh??" Then it shutdown. "uh oh" Now it won't boot back up "OH NO" My first thought is that maybe one of the CPUs was not perfectly set with its heat sink and went out on high temp or something. I unplugged and waited like 20 minutes. Still...no boot. The unit powers on but is just dead. What do I do next?