I've seen several problems listing problems with iMacs randomly shutting down, but NONE like this. My 21inch iMac arrived last week and it seemed to work fine. It had a lot of new stuff (I was using a 17 inch iMac that was 6-7 years old) I tried using the migration to transfer files, but because of some problem it didn't work. I had to use an Ethernet cable due to changes from the old to new.finally fished transferring files - no applications. Then the new started shutting down the only way to get it started was to turn the old back on. So, I shut down the old iMacs wifi, air port an removed the Ethernet cable. Here's the strange part . . . If I turn off the old iMac, the new one won't start. If I unplug the old computer, the ne one shuts down and won't restart. It's like the new one is entirely dependent on the old one. So, all you Mac gurus, what gives?