So I've been having trouble with my new iMac that i purchased recently (26th of August actually). Whenever I'm doing something CPU intensive, the machine just shuts off, but usually it's not right in the middle of whatever I'm doing, it's after I close the application. For example: I was playing SimCity4 the other day, pretty old game to cause this problem I would think. As soon as I exit the game, the system shuts off. No warning, nothing, just shuts off. This will happen when i close VMs (it actually happened yesterday while I was running the VM), etc... So I've reset the SMC/PMU, PRAM/NVRAM, and I've even reseated the RAM. Still the same problem. I've taken it in to a repair center in town, hoping I'll get it back by the end of the week. Does anyone have any idea why this would be happening?