IMac freezing intermittently--every few minutes. How can I fix this?

Question

A couple of days ago, I was browsing, and downloading something from Usenet, when my iMac all of a sudden froze up, grinding to an unbearable slowness. After trying to tolerate what was happening for 5 minutes, hoping it would pass, I finally gave up, and restarted the computer manually. To my horror, for about a day, I was plagued with the interminable locked up gray Apple startup screen, but thankfully the next morning, left it on from a restart to find later that the computer had managed to boot up to a login screen, everything seemingly fixed.

That was background. Now I have a different problem: My iMac is subjecting me to intermittent freezing episodes; I will be writing, or browsing in peace for a few minutes, before everything locks up, save for perhaps only the cursor. When the hanging is finished, the computer then resumes the missed operations (typing, etc.) in a hurry, as if one were watching a fast-forwarded video. Each hanging episode lasts from anywhere from 5 seconds to upwards of a minute; moreover, the system pops a window telling me that I don't have enough disk space for memory, though Finder consistently tells me I have upwards of 30GB worth of space (on a 250 GB HD). There's also another curiosity: When I tried using Software Update to update everything — trying to fix this problem — upon Restart it told it couldn't install a recent Security Update because "the source media [you?] are installing from is damaged."

What's my causing my problems? How can I fix them? Unlike a previous related question, I don't think this has anything to do with Youtube or my browser; closing near every window, including Chrome, has no solved the problem, or mitigated it in any way. I was also wondering could it perhaps do with something I downloaded -- could Trojans somehow associated with the movie I was downloading have anything to do with this problem? I'd really appreciate some help on this; this freezing has rendered a significant part of my workflow virtually unusable, and I don't consider myself very computer savvy.

Answer 1

It's very unlikely you downloaded something or broke everything with one download. Also - with at least 4 things not working well - please protect your pictures, emails just in case it's a hardware failure.

When only one thing is broken - it's often worthwhile to poke, learn, understand what broke and look for a fix of that one issue.

For any group of three or more problems, there's one solution that always works (and often saves a lot of time):

1. Back up anything you can't afford to loose and get someone who is a bit tech savvy to verify you have a workable backup that you can restore if needed.
2. Erase the mac and install just a clean system from the media that came with the mac.

This will quickly let you know if the hardware has failed. It will also solve nearly all software issues. Once you have surfed the web, made sure it is reliable, then you can run updates, restore your personal files and get on knowing it was just some corruption of the software.

Don't feel bad getting help from someone (even paid) if your savvy is for things other than a computer. A good tech can erase and install Mac OS X in 10 to 30 minutes. A good tech might take 4 hours to 4 days to pick apart all the things that could be wrong and tell you what happened. With multiple issues, it's hard to tell what was the root cause and what was just a subsequent failure.

It's often so much easier and efficient to just clean up the mess, start fresh, and keep an eye for any sign of the problems recurring. You will then have better data on the problem. You will also have a backup of your important files.

Since your computer can't tell if it has enough memory to run, (or is truly out of space) you can't really trust itself to fix itself which is why I jumped right to backup / restore for anyone on a situation as you describe. Also, if you were to determine exactly what broke, and did the fixes right, if it freezes or doesn't complete your fix - you will still be in the same badly working situation.

Best of luck - some good people have made answers with great advice here as to what could be wrong. I wanted to weigh in with a different sort of advice since no-one (you included) had mentioned protecting your data files.

Answer 2

You should check the Console logs.

My computer displayed these exact symptoms. The console logs displayed this error:

kernel[0]: disk0s2: I/O error

After reformatting the hard drive and locking out bad sectors, they went away for a time. Alas, they came back, and it seems I'll have to replace the hard drive which is likely failing.

In your particular case, you may be able to correlate the times of "stuttering" with errors in the log and determine what is causing the freezing. Good luck.

Answer 3

If this is something that's now happening regularly then it's likely a failed hardware component (which can get expensive if you don't have AppleCare (Pro Tip: go buy AppleCare and register your computer NOW (unless your Mac is more than 3 years old))). But it could easily simply be a corrupted filesystem. Boot from your Mac OS X install disk and run Disk Utility. Select your hard disk and run Repair on it.

If this is something that doesn't happen frequently (i.e., it happens several times in a row, but long intervals where it doesn't happen at all) then it could be a heat issue (you can enjoy the humor in heat causing your Mac to freeze). There are some temperature monitors that can run in the menu bar. Install one of them and keep an eye on it. If anything gets close to above about 175° F then it's too hot. Also, if the ambient temperature in the room your Mac is in is above 95° F it's likely that the internal temp of your Mac is too hot. Turn on the AC, buy some and point them at it, etc. Do anything you can to cool it down.

Also be aware that prolonged excessive heat can cause serious and permanent damage to your system.

But if it's not heat, then it's probably hardware. Backup your Home directory and take it to Apple.

Answer 4

Boot from the Restore DVD and check the drive. When all is fine create a new user and see if the problem exsist while logged in with that new (clean) User.

Case Problem gone? Softwareproblem. Time for Try and Error: Move all Prefs and Application Support items out of the Library of the Account and see if the problem is gone. Move the items back in groups till you know what item/pref cause the freezes. Basically you need to find the difference between the working user and the freezing user.

Case Problem not gone? What Bahamat said. Take it to repair.

Answer 5

I had the same problem with my IMAC. It turned out to be bad hard drive. I had bad experience with Genius bar at local apple store and local big stores to fix it. So I took it to a small local computer repair store. They replaced it with new hard drive and I am very happy ever since. HTH.