Diagnosing system lockups 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.
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:


Bad Processor
Bad Memory
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.