I am having a problem with my MacBookPro5,1 (more background below): the system will randomly lock up, with the following symptoms:

  • Screen freezes up, no corruption
  • System does not respond to keyboard or mouse input
  • System does not respond to pings over the network
  • No kernel panic message appears on screen
  • No messages in the system log

I have so far been unable to reproduce the problem at all. It happens both when I am actively using the computer and when it is idle; both when the screensaver is running and when it is not; and it doesn't seem to be related to any of the peripherals plugged in (though AirPort occasionally acts up). The system passes memory tests (memtest86+ and the provided Apple Hardware Test) so that doesn't seem to be it either. Is there anything I can do to obtain more diagnostic information?

Background. I recently had to replace the main logic board, after experiencing a problem where the laptop would not power up at all. Since then I have been experiencing random freezes and I would like to know if there's anything else that might need replacing, or if I should ask for another replacement for the main logic board while the repair is still under warranty.

  • Test the hard drive as well.
    – user479
    Commented Jan 10, 2012 at 5:31

1 Answer 1


Ask for another Logic Board diagnosis and/or replacement. There's really only three things that could ever cause failure this integral to the whole system simply halting all activity:

  1. Bad Processor
  2. Bad Memory
  3. Bad Logic Board

No matter what the result is, while you still have coverage after the recent replacement, something obviously is still wrong, and you should absolutely exercise your ability to have this re-diagnosed.

  • You forgot hard drive failure, especially if there is corruption where some of the system files are stored. That was a tough one for me to figure out on my iMac.
    – user479
    Commented Jan 10, 2012 at 5:31
  • In my personal experience, Hard Drive failure never locks the mouse from responding. Actions (clicks, etc.) may not do anything, but the simple act of moving the cursor still occurs. Commented Jan 10, 2012 at 5:59
  • I'm inclined to agree with Jason. System file corruption doesn't seem likely: I already tried reinstalling the OS.
    – Zhen Lin
    Commented Jan 10, 2012 at 6:11
  • I'm happy with your diagnosis. Just letting you know the HDD was the culprit in my case, locking it all up.
    – user479
    Commented Jan 12, 2012 at 22:17
  • Absolutely bizarre :/. Commented Jan 12, 2012 at 23:38

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