Shuts down unprompted while asleep

[Rantipole]

This has started happening to me recently. I've added no software since well before this started happening...

I will put my computer to sleep, and when I come back, say, several hours later, it will be shut down! I've checked the energy saver settings, and even made sure the "power button puts computer to sleep" setting, and everything looks OK.

I live alone, so no, this is not due to a prankster.

Any ideas?

(iMac G5 Rev A, OS 10.4.9? Most recent 10.4, it's been updated)

 

[Rantipole]

I've also reset the PRAM, and UNchecked the box in the Energy Saver preference panel which says "Put hard disk to sleep when possible."

Still shutting down after going to sleep for a while.

Please let me know there is something besides resetting the PMU which may fix this.

 

[ingenious]

Is it on a schedule by mistake?

 

[Rantipole]

Nope.

I have turned off the sleep function (so that the display turns off but comp does not go to sleep), and when this happens, my computer does not shut down. So it is definitely related to going to sleep, not simply inactive.

Apparently, my first gen G5 iMac is eligible for some sort of power source warranty extension. I'll probably have to go to my local Apple store and check if these symptoms are covered by that warranty.

 

[dcv]

Apparently, my first gen G5 iMac is eligible for some sort of power source warranty extension.

You can check the details of that here.

 

[Dave00]

Mine (iMac G5 1.8Ghz 20") actually does the same thing, only it happens immediately upon being put to sleep - put it asleep, goes to sleep for about 1/2 second, then immediately behaves as if I pulled the plug. It's been suggested to me that it might be a problem with the hard drive, but I ran fsck and repaired permissions, doesn't seem to be a problem there. I want to run Apple Hardware Test but unfortunately this doesn't work with my bluetooth mouse/keyboard.