Sudden shutdown

Since I installed OS10.8, my iMac has been shutting down while I am using it. it is very frustrating because I have lost data that I had spent much time inputting.

Is there a problem with 10 8 and if so how do I resolve it?

There's no problem with Mountain Lion. Many of us (myself included) are using it with an iMac. How about telling us which iMac you have? Year and model?

Generally, when an iMac is suddenly shutting down it usually can be traced to a hardware problem. For example: Bad power supply, bad memory, etc. The update to Mountain Lion and sudden shutting down could be coincidental.

My Imac is a 2007 2.4 g core 2 duo. I never had a problem with it before.

That's an older iMac (6 years old) and as I stated above, the sudden shutting down could be coincidental with the installation of Mountain Lion. It may be that your power supply has failed. Try booting the iMac into safe mode to see what happens. Hold down your shift key as soon as you hear the bong sound. Keep holding it until you get the spinning circle.

Gric said:

My Imac is a 2007 2.4 g core 2 duo. I never had a problem with it before.

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What OS did you have on it just before the Mountain Lion (10.8) upgrade?

- Nick

I had 10.7

Did you try starting in safe mode as I suggested above? Let us know what happens when you do.

You could try doing an SMC and PRAM reset:

SMC Reset
PRAM Reset

- Nick

By "shutting down" do you mean that OSX goes through the shutdown spontaneously, or that you lose all power immediately without OSX shutting down at all? (I suspect the latter, which points to a failure of the power supply, but it's important to know so we can try to get you to the right solution.)

My wife's '07 MB just had the power off on it's own disease a couple months ago - hers was a bad fan.

Would still try booting into Safe mode to check it out.

Yep, overheat and shutdown--bang! And the Safe mode is a good suggestion. Unless it's spontaneously closing down by software, it sound like a hardware problem.

Os x

You are right My computer was over heating . I changed my computer and OS is working right.

Gric said:

You are right My computer was over heating . I changed my computer and OS is working right.

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Just of the benefit of others reading this thread in the future what do you mean by I changed my computer?

Os x

What I mean is that I brought a new new iMac. Mine was old and it was time to upgrade to a 2.9 mhz iMac. It work great.

Well, that's one way to fix a problem! Congratulations on purchasing a new machine. Have fun and visit us often.