Did* you do that again? Could point to drive or memory issues. This is repeated in many web pages about the grey screen startup issues.
Also, is there some USB hub in use for such. Read https://www.lifewire.com/fix-mac-that-stall-on-gray-screen-at-startup-2260831 where this and more is covered.
There are some owners that get upset when you bring up the machine's age. It's well beyond the years I expect these to last. So while I would try what's in the article I linked to, it may be time.
*Note: Edited this word for grammar.
Hello - I've been all over the internet reading the history about the problem folks have had with the 2011 iMac booting up 50% and then going grey-screen.
I'm writing this new question to see if I can get more up-to-date info and to ask a few specific questions in regard to the specific attempts and results of the fixes I've tried to make...to no avail.
The iMac in question is: 27-inch Mid-2011. It's got: 3.4 GHz Intel Core i7, 16GB memory 1333 MHz DDR3, AMD Radeon HD 6970M 2048MB graphics card.
Here's what I've done so far: When I was able to get the computer to boot all the way I wiped the HD completely clean and reinstalled the OS and software. The machine worked for a while and then, while video editing (it's part of what I do for a living) the screen went blank again. No response. I tried to restart...it boots halfway the then the screen goes grey.
I've done all the methods of checking the machine on restart: holding "shift" holding "D", holding "Option+command+P+R", the whole she-bang. Hardware test - both the short and extended test, turn up nothing. The machine starts or doesn't in some crazy unpredictable madness.
You get the idea. So....I'm looking for recommendations on what to do.
Sorry for the long length of this message.

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