previous shutdown cause: -128

userCanceledErr = -128

What might have caused it, I haven't a clue.

See if the problem continues. If it does try doing a pram reset and also run Apple Hardware Test.

Another thing you can try is to disconnect all peripherals (external FWs, USBs).

Hi Baltwo!

Previous shutdown -128 happening on a 2.1GHz MacBook running 10.5.8, too.

Machine actually puts up the same "Are you sure you want to shutdown..." dialog box you get from pressing power button, with barely enough time to hit Cancel - if you're paying attention. Turn your back for an instant, and you'll miss it. Do nothing = off.

Completely random. Battery in good condition and at 100%, AC adapter plugged in and OK, replaced OS (A&I), Reset PRAM, SMU..... sure would like to know what -128 means! Only happens when left unattended for awhile (all sleep, screen saver and related functions set to never or off). "userCanceledErr," huh. What's THAT mean?!

Only other clue (maybe) was "Throttling respawn: Will start in 4 seconds. Arguments = (null)" and the only reason that caught my attention is because you _might_ have 4 seconds to cancel shutdown. Throttling respawn?

-128 Cause is a problem when a Mac shuts down because it runs out of power ( for MacBooks the battery runs out) If you have UPS, try unplugging it and directly plugging it into an power source. So if you plug it into a power source, it will never run out unless it is a hardware problem. I have a MacBook, and when it powers off suddenly I aslo get -128. Then when I power on, battery charge says Charging 1 %.