Black Login Screen

Now running 10.11.1 and still the same issue.

Hi Mike,

This issue has a couple of potential causes:

First try an SMC reset (this won't affect anything else on your iMac)

1. Shut down the computer.
2. Unplug the power cord.
3. Wait fifteen seconds.
4. Attach the power cord.
5. Wait five seconds, then press the power button to turn on the computer.

Then if that doesn't fix it, follow these steps while at the black login screen (i.e. instead of logging in):

1. Press the Power / OFF button once – this will bring up the dialog box which you can’t see
2. Press the “S” button – this is the shortcut to sleep the Mac
3. Hold down the Power button until a hard shut down is forced
4. Wait about 15 seconds, then hit the Power button again to turn it back on

If the above two tricks failed, an NVRAM reset is what is required.

1. Reboot the Mac and as soon as you hear the boot chime, hold down the Command+Option+P+R keys together
2. When you hear the boot sound again, the PRAM has been reset so let the Mac boot again as usual

Please let us know which of these answers resolved the issue for you.

-Max

Tried all 3 and no go. Same thing.

Strange. With the second one, you may have to adjst the first step if simply pressing the power button on you iMac doesn't bring up the Shutdown/Restart/Sleep dialog box - perhaps you have to hold it for a bit or something - and adjust step 1 accordingly. You'd have to experiment to see what brings up that dialog box for you when you can see the screen obviously.

New clue/data. I have a 27 inch Thunderbolt Display attached to it. When I unhook it and boot I see the lock screen! Maybe a bug with the Thunderbolt Display and 10.11??

That sounds even more like SMC now as that is directly responsible for external monitors. Going back to my first post, did you disconnect the power cord from the socket or the iMac? It's the iMac you need to remove it from. Also, try waiting more than 15 seconds - something like 20.

Finally, do you have AirParrot or Elitma SyncMate (or any other software with 3rd party kernel extensions that interact with display kexts) installed on your system?

Ok so I also have a Dell 27 inch monitor siting in a closet that hooks up via display port. I hooked that one up and took the TB display out. Same problem. Black Screen for the lock screen. Yes I did the first one and waited 20 seconds. I can do it again. But it seems not to like dual monitors on the lock screen.

Also to add to your second question I saw the posts on the Kexts stuff when I first ran into this earlier today and I have unloaded all of them so I have none now. Still have the issue.

Lots of people have your setup though, and you're the first to report this here, so I think there must be something about your system.

Unloading them only stops them until the next reboot. To see which are currently active on your system, please post the output of:

kextstat | grep -v com.apple

Obviously you'll need to run that before unloading any kexts.

Sorry I deleted the files and when I run the above command nothing shows up. So no kexts.

I am now leaving the iMac unplugged for a few miniutes.