iMac wont shut down or restart

[tocheskey]

Hi everyone, let me just preface by saying I apologize if this question and answer have already been posted somewhere else, the search function was down and therefore I wasn't able to do my due diligence. That being said...

I have a new, late 2011 21.5" iMac that runs beautifully except for one thing; it will not complete either a restart or shutdown process. The system will log me out of the user account and it will get to they grey screen with the spinner like its going to shut down or restart but then it will just lag there for as long as I let it. In an experiment one night I left it "shutting down" while I went to bed. When I got up 9 hours later it was still in the exact same part of the process as it was when I shut my eyes.

What is causing this, and please tell me that there is a very simple solution to this annoying glitch. I'm guessing that the answer is a wipe and reload of the OS (Mountain Lion btw) but I'm praying that there is a simpler solution. Any help anyone can provide is greatly appreciated.

Thanks in advance!

 

[DLary]

Does it start normally after you hold the power button down until it shuts down? If so, try to delete your caches. Search for cache cleaners (I use one called Mt Lion Cache Cleaner). This might help. The first shutdown after cleaning out your caches will still take a little while as some of the caches are rebuilt.

 

[tocheskey]

i tried that already and it didn't work. but to answer your first question, yes, the computer starts normally after i force a shutdown by holding the power button. thanks for your suggestion though!

 

[hfg]

Sounds like you have a program which doesn't want to quit. Have you looked at your startup processes ( SystemPreferences/Users/username/LoginItems ) for any unusual entries which you might remove.

First thing I would try is create a new user account without adding any features or programs. Re-Boot and login as the new user ... then try to shut it down. If it hangs here as well, then a reinstall is probably in your future. If it behaves normally, then it is in your account and you can either decide to try to remove things until it works, or start over with a new account and add things back, hopefully not having the shutdown hang reappear.

You could try doing a TimeMachine backup of your existing system to a external disk, then after you reinstall the OS, let the System Assistant restore from your TM backup. This may simply bring the problem back with your data, but you might get lucky and the problem goes away without having to reinstall everything.

-howard

 

[elduderino69]

having a similar problem.
I'm running an early 2008 iMac 2.66ghz with Lion.
I'm noticing many times after my computer has been on i can't use half of the main apple menu. i can check for updates, get to system prefs, apple store, but about this mac won't work, sleep shut down, restart, log out...

Also sometimes the power button won't put it to sleep, its like nothing happened.

I've been running shut down commands into terminal but i'd like to get to the bottom of this.

It may be nothing but I've noticed it more since I started using the automatic sleep timer in Energy Saver.

any further ideas? I've tried clearing the cache, but no luck. it's looking like a reinstall is my only option? please tell me otherwise, thanks

 

[PlanBe]

Zap the PRAM and reset the CMS

Zap the PRAM and reset the CMS

A small amount of your computer’s memory, called “parameter random-access memory” or PRAM, stores certain settings in a location that OS X can access quickly. The particular settings that are stored depend on your type of Mac and the types of devices connected to it. The settings include your designated startup disk, display resolution, speaker volume, and other information.
1. Shut down the computer.
2. Locate the following keys on the keyboard: Command (⌘), Option, P, and R. You will need to hold these keys down simultaneously in step 4.
Turn on the computer.
3. Immediately press and hold the Command-Option-P-R keys. You must press this key combination before the gray screen appears.Continue holding the keys down until the computer restarts, and you hear the startup sound for the second time.
4. Release the keys.
Resetting PRAM may change some system settings and preferences. Use System Preferences to restore your settings.

How to Reset Your Mac's SMC

The method for resetting your Mac's SMC depends on the type of Mac you have. All SMC reset instructions require shutting down your Mac first. If your Mac fails to shut down, try pressing and holding the power button until the Mac shuts down, which usually takes 10 seconds or so.

Mac portables with user-removable batteries (MacBook and most MacBook Pros):
1. Shut down your Mac.
2. Disconnect your Mac portable from its MagSafe connector.
3. Remove the battery.
4. Press and hold the power button for at least 5 seconds.
5. Release the power button.
6. Re-install the battery.
7. Reconnect the MagSafe connector.
8. Turn your Mac on.

Mac portables with non-user-removable batteries (MacBook Air and some late 2009 MacBook Pro models):
1. Shut down your Mac.
2. Connect the MagSafe power adapter to your Mac and to a power outlet.
3. On the built-in keyboard (this will not work from an external keyboard), simultaneously press and hold the left shift, control, and option keys while you press the power button. Release all keys at the same time.
4. Press the power button to start your Mac.
5. Mac desktops (Mac Pro, iMac, Mac mini):
6. Shut down your Mac.
7. Unplug your Mac's power cord.
8. Press and hold the Mac's power button for 15 seconds.
9 .Release the power button.
10. Reconnect your Mac's power cord.
11. Wait five seconds.
12. Start your Mac by pressing the power button.

**Alternative SMC reset for Mac Pro: If you have a Mac Pro that isn't responding to the normal SMC reset as described above, you can force a manual SMC reset by using the SMC reset button located on the Mac Pro's motherboard.**
1. Shut down your Mac.
2. Unplug the Mac's power cord.
3. Open the Mac Pro's side access panel.
4. Just below the Drive 4 sled and adjacent to the top PCI-e slot is a small button labeled SMC. Press and hold this button for 10 seconds.
5. Close the Mac Pro's side door.
6. Reconnect your Mac's power cord.
7. Wait five seconds.
8. Start your Mac by pressing the power button.