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.
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.
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.)
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.
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