Hi Virtual
Thanks for answering. I don't think it was that, but you could be right.
I think - though I could be wrong - that I pressed the power button once too often while being worried that it wouldn't start up, and it was Mac's way of shouting STOP DOING THAT.
Re: the firmware update it did just download, I didn't have to press the power button to start it up again.
Regarding Software Updates from Apple: I have a look at what they are, and know that some of them don't apply to me. So I uncheck them. Next time I run Software Update, there they still are, eager to be downloaded.
I've checked around the net about the iMac power button, but my question is too vague or stupid to get an answer, I think.
ps. I also didn't know that iMacs have fans. There are 4 iMacs in this office and I've never heard them. Where would they put a fan in a stainless steel enclosed iMac which is only 1" deep?
(gets up and takes a sideways look: ok, it's deeper than 1" behind the screen, and there is some slot behind the screen, at the top, which I've not noticed before. You wouldn't would you? Is that the fan outlet?)
You may think I'm talking gibberish, but we all have learning-curves, despite having used Macs exclusively for over 20 years now...............
