Hi people of this wonderful forum. I've been having a weird issue that I tried to track down for quite some time already, but I haven't been able to find a solution, nor I managed to find any thread of anyone having the same problem, so I decided to try my luck here. My trusty 27" 2.93 Core i7 Mid 2010 iMac started to restart randomly about a year ago. Maybe not exactly randomly sometimes it restarted itself sometime during the sleep process, usually in the middle of the night. It NEVER did that on any other occasion (under load, when waking up.. nada). I saw it a couple of times when I happened to be awake - sounds like it's about to start up, but it shows the grey startup screen and plays the chime instead. It was rare in the beginning, but the frequency kept increasing to almost once a day. Since the computer was already generally slow due to software bloat, when Mavericks came out I decided to take the pragmatic approach and reinstall the system clean to speed things up and possibly rule out a software problem causing these restarts. It worked great for about a week but then it appeared again. It restarted itself in total of 5 times since the reinstall. I saved all logs from the events: http://pastebin.com/vkfESyJp http://pastebin.com/1mEYbLMA http://pastebin.com/mwermcx2 http://pastebin.com/8qKrtyYb http://pastebin.com/wd9TZpZY I tried running the Apple hardware test in the "extended" (or whatever it's called) mode resulting in no errors (I upgraded the ram to the 16GB kit by OWC, though). I'd appreciate any help by anyone able to dig through the logs. Thanks.