Mountain Lion won't wake from sleep

Holding the power button forces it to shut down, not wake up. Any key (I use space) should wake it up, but it doesn't?

I've got the same.

After opening the lid, or press keyboard to wake it up, I see that computer is starting, making noises from speakes but screen stays black.

I've got clean 10.8 instalation (from usb disk). MBP 6.2, Mid 2010.

I've got problems with iPhoto: https://discussions.apple.com/thread/4177063?answerId=19165167022#19165167022

Since I upgraded to 10.8 I have started experiencing the same problem on my mid 2011 iMac 27", usually only if it's been asleep overnight. It is still powered on (things plugging into the USB ports are still charging), but the screen doesn't come on, so I have to hold in the power button to kill it, and then start it up again. 10.7 never had this problem.

My mid-2010 iMac is not waking up overnight after installing ML. Unlike leonjanzen, mine won't even charge the phone over usb. Feel like beta testing OSX for Apple all the time on this 10 year old OS.

Edit: btw, the PSU stays hot even tho it won't wake up. 😠

Hi,

Please perform an SMC reset.

1. Shut down the computer.
2. Plug in the MagSafe power adapter to a power source, connecting it to the Mac if its not already connected.
3. On the built-in keyboard, press the (left side) Shift-Control-Option(ALT) keys and the power button at the same time.
4. Release all the keys and the power button at the same time.
5. Press the power button to turn on the computer.
   Note: The LED on the MagSafe power adapter may change states or temporarily turn off when you reset the SMC.

Source: http://support.apple.com/kb/HT3964

Thanks wfrschulte, but that didn't work for my 2010 iMac 😟

I have an early 2008 Mac Pro, it's crashing and/or won't wake up from sleep since installing Mountain Lion.

At first it wouldn't go into deep sleep at all, now with 10.8.2 deep sleep works again but it won't wake up!

I have a 2009 MBP and had no problems with lion. I wish I never bought Mountain Lion.

Anyway, mine wakes from sleep UNLESS I have my external monitor plugged in. Then if I haven't woken it up in over an hour the fans are full blast and it will not wake up.

I've done all the usual: permissions, smc, pram, and a couple others I've found on the net.

As usual, doing those things gives me no joy.

What happened to it just works?

That may be related to the issues people are having around external drives unmounting after sleep. I sometimes have the same issue when a specific Firewire drive is connected, then I can only wake up my iMac with the power button.

My guess it that Apple made many changes arounf power management to implement PowerNap, and that this creates some of those new issues as side effects.

Very annoying...

I did a lot of hunting but missed the external drive issue.

I do have 2 external drives hooked up.

I'm going to try disconecting them before I sleep my computer and see what happens.

Thanks for the input!

Thanks for suggesting the SMC reset, but unfortunately it hasn't helped on my computer. I don't have any external drives hooked up either. I do usually have two phones plugged in for charging, but they aren't mounted as drives when I put the computer to sleep, so they shouldn't be affecting anything either. I updated to 10.8.2 last night, hoping that the problem might be fixed, but again this morning it wouldn't wake up. 😟

@fkoehn, @manfromspace:

Ok, it's good to read all of this. Mine's a 2009 MBP with a recent "upgrade" to ML. Same set-up with 2 external FW drives and an external monitor. My mac has yet to wake from sleep in the normal way. I've always had to force shutdown and re-start. It was interesting to read of the same issues with similar set-ups.

Is the SMC reset a viable option?

Thanks in advance.

Same here. Also have a 2009 MBP and just upgraded to ML yesterday. Tried to reset PRAM, SMC, repair permissions...I had NO problem with Lion! This morning I walked to my laptop and the fans were full blast, screen was black, and the the sleep light indicator was not lit...MBP was not responsive to usual depressing of keyboard keys to wake....I had to hold power button down to turn it off then restart. I've got not external drives connected directly, only external monitor. Will have to try to remember to disconnect it before going to sleep tonite.

I'm having this same issue after the latest update of Mountain Lion. Just thought I'd chime in here to monitor the thread for a suggestion that a fix is coming.