9 Replies Latest reply: Apr 26, 2009 5:00 AM by Shane Reynolds
Phil Sinatra Level 1 (0 points)
My iMac occasionally experiences a slow shutdown after being used for a few hours or more. When this happens the following startup locks up either on the grey apple screen, or the blue screen that follows. It seems to happen when I have been using the computer for more than an hour.

2 ghz intel core duo
4 gb memory
osx 10.5.6

Anyone know what causes this?

imac, Mac OS X (10.5.6)
  • Carolyn Samit Level 10 (103,365 points)
    Hi Phil,

    Have you tried booting from your restore disk?
    Restart your Mac while holding down the C key, pressing the power button and inserting your restore disk all at the same time. An Installer window will open, but do not proceed with any installations. Instead, from the Menu Bar, select Utilities > Disk Utility. In the Disk Utility window click First Aid, and then click Verify. If Disk Utility reports errors, click Repair. When Disk Utility is finished, from the Menu Bar, select Utilities/Startup Disk. Select MacintoshHD 10.x.x and click Restart.

    If the boot disk "appears to be ok" ... how much free drive space is there? Right or control click the MacintoshHD icon on your Desktop, then click: Get Info. In the Get Info window, click the discovery triangle so it's facing down. You will see; Capacity and Available Make sure you have 10% available disk space, 15% is better. Insufficient available space, can cause performance issues, system corruption, and possible loss of data.

    Some links that will provide more information on maintenance.
    Maintaining Mac OS X

    Leopard Cache Cleaner

  • Phil Sinatra Level 1 (0 points)
    Hi Carolyn
    I have booted from an external drive and have run Disk Utility, Disk Warrior, and 3 other similar programs designed to verify the disc, they all came back with no errors.

    The computer is only a year old, the hard drive is not even half way full so there isn't any type of space issue.

    I regularly run Onyx ever month or two months to clean the cache files and do general maintenance, I am really at a loss as to what the problem could be.
  • Carolyn Samit Level 10 (103,365 points)
    HI Phil,

    *"and 3 other similar programs designed to verify the disc, they all came back with no errors. "*

    Did you run the Apple Hardware Test from your restore disk? Go here for instructions.

    You could do the 10.5.6 combo update available here:
    Following that make sure and repair disk permissions.

  • Phil Sinatra Level 1 (0 points)
    I do have the combo update already installed. I will try the hardware test this week to see the results. Could it be a heat related issue due to the fact the computer is on for a few hours as opposed to only 30 minutes or so?
  • Carolyn Samit Level 10 (103,365 points)
    Let us know the results of the hardware test. If it's heat related due to having the computer on for a few hours then something is way wrong. Even if the hardware test comes back ok, I'd take it in for service.

    Make sure and back up all your personal data first in case it's the hard disk failing.

  • Zachnap Level 1 (10 points)

    When did you purchase this iMac? Early/Late 2006 or early 2007?

    This is probably the same problem that thousands of other iMac users and myself are experiencing who bought the system in this time-frame. It is looking like a heating issue and all you can do is delay the inevitable failure of your computer by running SMCFancontrol. There are numerous threads running on these boards, blogs, and other mac forums about the issue.

    Here is a link to one of them:


    Apple is telling people that it is not a "known issue" and having them fork over $1000 a pop to replace the mainboard. IOW, the are better off buying a new computer.
  • Phil Sinatra Level 1 (0 points)
    I bought the computer at Xmas of 07. This past January the one year warranty ended and it is almost exactly when the problem started. I am no convinced the issue is heat related because it typically does not lock up while I'm working, instead it experiences a slow shut down and a lock up on the next boot. This happened last night for example:

    Turned computer on, no problems. I ran Handbrake on a movie which took about 2 hours. When the process was over I let the computer sit for a few minutes, and then shut it down. When the shutdown process begins, rather than a typical shut down which takes a few seconds, the computer displays the "spinner", similar to the little animation that appears when you boot the computer on the grey screen under the apple logo. It spins for a significantly longer period of time, let's say 20-30 seconds before shutting down. I started the computer up again within 5 minutes, and it locked up on the grey screen with the apple logo. I press and hold the power button to force a shutdown, count to 10 and start it up again, and it boots up no problem. It is like there is some process or something that is running when the computer has been on for a while that is not stopping properly or screwing up the next boot up sequence. Once that has been flushed out, it boots fine.

    Does that make any sense?
  • Phil Sinatra Level 1 (0 points)
    Extended hardware test comes back with no errors.
  • Shane Reynolds Level 1 (5 points)
    I had the EXACT same problem this morning. My computer was on for most of yesterday updating some songs to iTunes + and downloading a TV show for my son. I have 1.5mbps DSL (the fastest I can get thanks to AT&T), so it took a while. I then set Chronosync to sync my iTunes with my MBP downstairs before we left for church; point being that the computer was on for most of the day. When I shut it down, I went to brush my teeth and it was locked when I got back, so I held down the power button to get it to shut down. My two FW800 drives did not turn off, so I had to unplug them to get those bright lights to turn off. This morning, my iMac would not boot, locking several times on the grey screen with the activity spinner stopping. I forget what it's called, but I unplugged the computer and held down the power key for ten seconds, then I zapped the PRAM. The computer then booted fine, and I plugged in the FW800 drives and everything seems to be fine. This is a six-week old 24" 3.06GHz iMac. I am troubled by its "bugginess" so far, BUT I am optimistic that 10.5.7 will bring joy and happiness back to my Apple ecosystem.