Mac suddenly restarts with no warning

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Level 2

153 points

Mac suddenly restarts with no warning

Starting about two weeks ago, my Mac Pro has exhibied a very intermittent but serious problem: suddenly, with no warning, the screen goes blank for a moment, then the computer shuts off and restarts immediately. Once restarted, no error message or other indication of a problem appears.

I do not think the problem relates to heat. The room is quite cool, and the machine is mounted in an open area out of the sun. I do not notice unusual fan activity before or after the restart.

I am not certain, but I strongly suspect that each time, iTunes was playing a video while I was undertaking other tasks. Certainly that was the case the last time the machine restarted. I am almost certain that iTunes was running video the other times, but I am not sure. The restart is so sudden -- surprising -- that I am not in a position to preserve data on what I was doing before the restart.

Recently, in about the last two weeks, I noticed a problem with iTunes playing .m4v files created by Handbrake. The videos play fine in QT. Is there a common thread?

So far, I have not lost data.

Mac Pro 2.8G, APPLE STOCK 4G RAM & NVIDIA GeForce 8800 GT, Mac OS X (10.6), HP w2408h 24" monitor

Posted on Oct 26, 2011 9:15 AM

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Answer 1

Oct 26, 2011 9:56 AM in response to Zardon

To get a better handle on this problem, you may want to turn off the Energy Saver Preference "Restart automatically after a power failure" This will give you more separation in the time-stamped logs between shutting down and starting up again, and make messages more clearly attributable to shutting down.

The Mac Pro uses a unique power cord that has a large block of rubber around the computer-end. To remove this as a distraction, disconnect the power cord and jam it back into the back of the Mac as hard as you can. In the US and other 110 Volt countries, you can substitute a different power cord without the big rubber block, as long as it is not a lightweight one.

Next, take a look at this article on reading out kernel panic logs. Go see if you have any stored kernal panic logs. If you do, cut and paste the text here (not a screenshot).

Mac OS X: How to log a kernel panic

If no kernel panics, use Console utility to see if there are any console messages leading up to the time of the failure.

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Answer 2

Zardon Author

Level 2

153 points

Oct 26, 2011 1:51 PM in response to Grant Bennet-Alder

Thank you. I always have "Restart automatically after a power faillure" turned off. (Unchecked.) To be certain, I went to System Prefs and confirmed that to be the case.

The power cord idea is a very good one. I did as you said. We'll see. If it happens again and remains unexplained, I'll try a different power cord.

I checked out /Library/Logs/DiagnosticReports. (I have OS 10.7.2.) I did not find any report with the words Kernel or Panic in them, although there were several reports logged for yesterday and today.

The two most recent reports are typical of the report names I found:

bash,bash,grep,grep,kextstat,kextstat,prl_disp_service,prl_net_s_2011-10-26-1220 38_localhost.shutdownStall Today 12:20 PM

SymDaemon_2011-10-25-110916_localhost.crash Today 12:22 PM

Note: I turned the computer off at about 12:20 today. It did not, to my knowledge, crash at that time. The sudden restart happend earlier this morning, at about 9:00 AM, I would guess.

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Answer 3

Linc Davis

Level 10

209,739 points

Oct 26, 2011 4:37 PM in response to Zardon

This sort of issue is usually, if not always, caused by a hardware fault.

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