I downloaded Mountain Lion OSX three days ago. On start-up my IMac shows a black DOS screen. Must unplug the Mac to restart. Please help!

Hi,

Can you also tell how to to turn off bluetooth devices during booting?

After you have posted this, I am going to test this and will reply here.

Don't turn them on to begin. I mean the mouse and keyboard.

Ok, is it that easy?! 😁

I was already looking for some startup files... 😝

Thank you very much for your reply! 😉

It's a quick fix, but yes.

Funnily, I had a similiar problem with another iMac (late 2011) booting in safe mode in Lion which I also corrected by not turning on the bluetooth devices before it was fully booted. This was properly solved by a recent firmware update, so I would hope that something similar will be done for Mountain Lion and my older iMac soon.

I had the exact same problem.

If you use a wireless keyboard and mouse leave them on all the time don't switch them off when you shutdown.

This will probably solve the issue until a fix comes out.

Unfortunately, for me that did not help...

Hello!

I also have the same problem as reported here in my Mac Mini (Early 2009). It was not fixed with three different ML updates (the last a clean installation), or with varied suggestions here and in other forums (reset PRAM, safe mode, Bluetooth...).

Waiting for an update that fixes it! 😠

I just installed the 10.8.1 update and it does not fix this issue! Sad but true... (maybe in 10.8.2 ?) But: If I turn off bluetooth before I turn off my MacBook Pro (5.1) it will boot normally next time.

Greetings!

Someone posted the issue goes away if you don't turn on your connected Blutooth devices (keyboard & mouse) before boot up. I think you can turn on the Blutooth devices when the grey screen pops up because this is after the initial "Power On Self Check" or whatever it's called.

I was having this "Black Screen of Death"... well, not really "Death" but it was annoying haveing to type "exit" from what looked like a DOS screen on a Mac. 🙂

I was having other issues with Internet connectivity too. Could connect to the wifi easily enough but the internet connection would hang after a little while. Could not access Software Update or any web locations via Safari. I had to SMC, PRAM though a simple Restart would work some of the time. It was as if the some conflicting module would load at some point causing the Internet connectivity to hang.

I had been messing around with my Users directory while moving it to an external disk array so I errased "Macintosh HD" and installed OS Mountain Lion again from scratch - a clean installation.

After this clean installation I was still having the problem of the Internet hanging until I hooked up the Netgear Gateway to an Apple Time Capsule, wich seems to have stabilised the connectivity somewhat. I intend to connect the AppleTV and any other networked devices to this Time Capsule Hub and use it's 1TB internal drive with Time Machine if I decide I don't mind plugging in an additional exteral drive like a Seagate GoFlex.

Anyway, I'm using an early 2009 iMac and the Single Boot (black "DOS-like" screen) and WAN instability seem to have been eliminated... for now.

Hi,

I have an late 2009 iMac and I recenlty downloaded Mountain Lion and I'm also getting a start up error message !

Looks just like the picture that the person took.Hope they fix the issue soon.When I first saw it I did a double take and thought this reminds me when I had an HP pc and running windows vista ouch !

I now also have this issue when bluetooth is turned off, just like most of you...

Yep, same problem. Late 2009 iMac now starts up with the black screen,

https://discussions.apple.com/thread/4236515?answerId=19368610022#19368610022

well the problem disapeared until today when I installed the latest mountain lion update. Now it's back the nice black screen !

After multiple tests I found a way to not display the black screen on start: turning off my bluethooth devices (magic mouse and keyboard) after the Mac stop and only turn them on after the apple screen appears the second time during start or when the desktop appears.

This works for me!!!! 😉