After startup my iMac's screen turns black

I Am also having the same problem . I have a 27" IMac . I have updated to OSX Mavericks . goes threw start up then goes to the black screen with mouse . Contacted apple even tho its out of warranty with Apple care . I have spent close to 3 hours over the phone with them the past couple days . Tried command after command . sat we re downloaded the OSX mavericks onto the iMac . Same problem again . Last night erased the hard drive and re downloaded software . Then went to go to re backup from time machine . It then told me there was incompatible software I'm guessing from the time machine ? Going to call later this evening to see what else we can do . The apple tec told me that there computer people are working on a resouoltuion to the software glitch . She said most computers come back going threw the 1st couple of techniques . And some just don't want to . I'm guessing I'm the lucky one . With a 2k paper weight !

Thanks aapleman! Your advice worked and all I had to do was wait patiently. I was a little skeptic at first to if it would work or not, but it's doing fine now!!!

I got this problem too - after upgrading my early 2008 Intel iMac to Yosemite.

I tried all the tricks in this thread and got nowhere.

The only thing I found that could get be logged in was to use Command-R at start-up and then reinstall Yosemite over the web. But this takes many hours and was short-lived because the black screen would reappear next time I logged in.

I then had a long conversation with Apple support where we tried all the tricks again, but none worked, until they suggested the following:

1. Use Command-R to reinstall Yosemite

2. Log into computer and back-up everything to Time Machine

3. Restart with Command-R again

4. This time, go into Disc Utility and erase the entire hard drive

5. Reinstall Yosemite on the clean system (i.e. don't select the Time Machine back-up)

6. Restart computer

7. Computer will start-up with clean system. Select option to restore everything from your Time Machine back-up.

The above took me several days dues to the amount of downloading and back-up, but has done the trick. Operating system works fine now, with no black screen at start-up.

This is a terrible problem, so good luck!

Just restart the computer. I had the same problem.

Hi

I'm no tech expert, so forgive my rudimentary grasp of the situation, but I've experienced this problem a lot since the Yosemite upgrade.

Perhaps my experience will help you or others with the same problem.

First, on my old iMac 27" (2009 model) although this was a white screen with cursor only, and now last week on my new 5k iMac (this time a black screen and cursor).

If I have the same problem as you, the iMac starts up, shows the Apple logo, and then the status bar begins animating to show that the system is booting up.
At about 30 percent, the status bar disappears, and the screen goes black.

After a lengthy call with Applecare, we seem to have solved the problem, and it was actually pretty simple.

Start the machine in safe mode (holding shift on start-up if you're new to all this).

iMac should start up properly, although will be a little glitchy.

At user screen, log in as usual, and let the desktop load.

Then open up System Preferences, and go to Users and Groups.

Click the lock and enter password to give permissions.

Under Login Items, try deleting all the items in the box.

Then click on Login Options (bottom of User window).

In Automatic Login - toggle to your specific username.

Click lock to save, and restart.

This SHOULD clear the error that was causing the issue.

I found that it helps to repeat the steps above and toggle again to switch Automatic Login back on.

I'm not entirely sure, but it seems that the additional functionality that was added recently around login options seems to have caused some sort of issue, where the machine can't decide whether to give you automatic access, or the option of guest user. This clash means the iMac simply opts not to offer any options at all. Hence the black screen.

Hope this helps. And thanks to Martin at Apple for patiently solving my problem.

GDI,

Thank you for your wonderfully helpful and beautifully documented fix. It completely solved my boot up problem. Thanks to users like you who take the time to share what you learned from an Apple support rep, we don't have to go through the same pain you did.

Thank you!

Found this and it worked.

http://www.networkworld.com/article/3012241/macs/a-fix-for-the-os-x-black-screen -of-doom.html

Bless you!!!! Had taken my iMac to a family members and had surges in the night and thought I was fried.... It took two tries, but this worked. You saved my holiday spirit ;-)

Thanks!!!! You are great!!!!!!

Have you ever left your iMac at the Apple store in Westchester for them to fix? When I