My 2012 27″ iMac screen went black while using it. I waited, then pushed the sleep button, and then again to wake it. I saw a gray screen with the apple logo with 5 pink vertical bands, about 1″ thick. Thinking my graphics card had gotten jacked up, I waited, but then forced a shutdown. When I rebooted, I saw the normal gray screen with apple logo (no pink bands) and then my login screen for both my accounts. I tried logging in, and got a progress bar under the account picture. It went about 50% across, then the screen went completely gray again (no pink lines) and has been sitting here for several minutes. I tried restarting again and logging in with the other account, and get the same progress bar to 50%, then gray screen. Is there an update happening? Should I pull my time machine drive/ disconnect it to safeguard it? I will give it some more time and see if it ever decides to log me in. Nervous as he**
Ok,, update: screen started flickering very quickly, for 1-2 seconds, then back to gray screen. What in the world?