Hey guys - I have a 2011 27" iMac / 3.1ghz i5 / 256SSD(Apple installed) + 1TB / 4GB factory. I received an 8GB Crucial upgrade kit to take my memory to 12GB total. I placed the Crucial ram in the bottom available slots and started up. Approximately 10 seconds after logging in (and my start-up programs started, including activity monitor) the system will just turn off. It makes no noise, just turns off and begins to re-start. I restarted twice and got the same result, crash and restart 10 seconds after logging in. It should be noted I could see in the activity monitor that it was reading 12GB of memory installed. On the THIRD crash and restart everything was fine. It started like normal, all my programs loaded and it never crashed. I checked system profiler and everything was registering properly. That night I shut it down and went to bed. The next morning I started it up and it began crashing again. I thought the memory might not be seated properly so I took out all four modules and made sure they were installed properly again (I do know what I'm doing). I started it up again and it crashed the same way as before. I decided I wanted to shut it down when it came to the log in screen instead of let it keep crashing again. I hit SHUT DOWN on the log in screen but it would not shut down, it kept restarting. I tried hitting shut down several times but it would restart each and every time. I finally had to pull the power cord to get it to stay off. I started it up about an hour later and everything was FINE. Everything loaded great, showed 12GB installed and no problems. It worked for about 24 hours straight, even after restarts and coming back from sleep. This morning I booted after shutting down last night and it started crashing again. I let it go 3 times then pulled the Crucial memory. It started back up fine with only OEM memory and has been great even after several re-boots. Anyone ever heard of this?! First, the issue of it crashing. Second, why will it work ok for several hours then crash on the next re-start. Third, why is it restarting even when I hit shut down? I'm guessing I just need to exchange the memory but I wanted to get some opinions first. Thanks!