I'll have to try that specific sequence.
To date this is the situation:
1.) Machine always starts in AM, runs fine all day; in either OSX or XP.
2.) Machine always starts after exactly 18 minutes of shutdown.
3.) Once started and allowed to load completely it will not shutdown via the power button.
4.) After full boot the machine will power down normally using the keyboard or mouse click commands.
I installed a new Seagate, 320GB HDD over Christmas, but this anomaly only began about 2 weeks ago.
Any info is more than welcome. This is my business laptop & I'd hate to have to ship it to Apple for an extended period. I'm beginning to think that this may be more involved that a simple power button issue. Perhaps, a bad capacitor or diode?
Our symptoms are not quite the same, but they do share some common attributes... e.g., "starts after exactly 18 minutes" certainly suggests a process timeout rather than a thermal hardware intermittancy, which is never that predictable. Something that interacts with the PMU firmware would first come to mind, but I'm just guessing, since I know nothing about the internals of the OS. I'm sure that many of the people on this forum do, though. Sorry I can't be more help.