I bought an i-mac DV special edition (graphite colored) about a year ago, and I have been ver happy with it. However, a couple months ago something happened that convinced me my computer was evil. Around 12:00 at night I woke up to find my computer on. Thinking I had accidently left it asleep, and it had just woken up I turned it off, and went back to bed. No sooner did my head hit the pillow then I herd the BOING start up sound that macs make. After screaming loudly I ran over the my computer, and yanked out the power cord. From that day on I always pull out the power cord before I go to bed. I talked with my father, who also has an i-mac DV speical edition, and the same thing happened to him exactly. He woke up the find it turned on, and after he turned it off it turned on again by itself. This also a couple of months after he bought it. Has this happened to anyone else’s computer? Or are all the computers in my house possesed? Anybody have any idea why it happened?
i’ve seen computers restart instead of shutdown, usually due to errors in the way the bios handles different sleep states. also, if you’re on a network, there’s a little thing called ‘wake on lan’ (wol), where a computer can be powered on by another system on the network (if it’s asleep, not off). but you usually have to be running software that will allow that.
I knew it all along: Imacs are evil and not to be trusted! Soon, your little computer will be devouring small animals and hunting for other of its kind, so it can reproduce and spread the floppyless computer system worldwide! They told you to ‘Think Different’. Soon, thousands upon thousands of imacs will ‘Kill Different’, waking up after you thought the carnage of their primitive GUI and nonexistent system management tools was over, spreading havoc, a chaos fuled by the power-crazed Motorola chips they have. Nobody will be safe! No user will be able to customize his own system! Adding a hard drive will be as complex as filing a tax return! And thousands upon thousands of script kiddies will think they’re Real Programmers ™ just because they can pound out an AppleScript that runs an image viewer and opens some cheap porn! The horror! The horror! AAAAH!
::swats Derleth::
Cartoongod, I too have a iMac DV SE, and I’ve never had the problem you describe, but this is because I’m almost always awake and have the computer on at midnight anyway. 
Off the top of my head:
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At midnight every night my computer starts updating its index. This is a feature of Norton Utilities’ File Saver (I think). It’s does this automatically, every night. You might not have NU installed on your iMac, but I thought I’d mention it because of the time coincidence.
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Check your Software Update control panel to see if it’s set to automatically download software updates off the 'net. If that’s not it, poke around your other control panels to see if anything’s set to do something automatically at that time.
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What’s your home setup? Are your two iMacs connected to each other, or to any other computer/peripheral? The problem could be there… somewhere…
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Check your power button. I faintly recall a TIL article that addressed that some iMac buttons may be “sticky”, causing various problems with turning the computer off and on.
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Any pranksters around? A computer won’t turn on by itself unless it’s receiving instructions to do so. Any mysterious AppleScripts lying around? How’s your virus protection?
If that yields nothing, get an exorcism performed.
You do know you should never turn your computer off by yanking the power cord, right? Wait for it to finish starting up, then shut it down, and then unplug.
I tried a couple quick searches at the Apple Tech Info Library, but I didn’t find anything using the keywords “iMac turn on automatically”. Give it another whirl, though; you may uncover something I didn’t.
Good luck.
I don’t know if this is true of the iMac, but I’ve seen computers that can be turned on (from a complete “off”, not just sleep) by hitting the space bar. Do you have cats, perhaps, or anything else that might bump the keyboard?
At least it didn’t turn on AFTER you pulled the power cord.
I had this happen to my TV. It would just turn on, the volume would go all the way up, then all the way down, then turn off. Freaked the hell out of me.
But it may be just something with the power in your house.
And why do you care? Just leave it on all night, no harm done.
Check the forums over at http://www.macfixit.com/cgi-bin/ultimate/Ultimate.cgi?action=intro . Ask your question, and look in the forum archives. That is a great place for answers to Mac problems. Better (in some instances) than Apple Support, at least in my case.
Well, aside from being haunted which is a very real possibility, I think most Macs have a feature where you can set it to turn on automatically at a given time. Given that it’s turning on at 12:00, I’d say it’s a combination of auto on and VCR syndrome (digital clock set to midnight).
It can be a maintenance program, or wake on modem call [phone rings, computer comes on], etc. Check your settings.