Hi. I have a iMac 2012 27" Core i5 in Brazil. About 3 months ago it becomes to turn off unexpected, and I have to take the plug off for 15 minutes and then restart every time it happens (1 or 2 times per day). After some tests, I think it's possible to be some USB problem, because when there are no devices plugged in, it not happens (can be a coincidence). Apparently, it's not because of the device, but the port. It happened with somebody else? Somebody heard about a USP port problem (a short circuit, for example) in iMac? Thanx.