10.8.2 External Display Issue

correct, this solutions works...however if you were to put your laptop to sleep, when it wakes up you are back in the same situation as before, unless you reboot and close the lid as it boots up again.

It works fine in my case even after i put MBP into sleep. After the first power on, did you move MBP from external display setup ?. In my case as long as i don't move my MBP from external display setup, it works fine even after waking from sleep.

Same issue.

I switch a lot between builtin-screen (when travelling) and single external display which makes this 'feature' terribly annoying. I have to restart my machine twice to three times a day, and it's not even running Windows.

The nvram setting seems to get lost somehow which really isn't supposed to happen, it's called non-volatile RAM for a reason. This leads me to think something is overwriting that setting so we'd need to figure out a way to see who and what is touching nvram's boot-args.

Exactly. and before 10.8.2 it worked all the time, even when you switch between external and internal displays.

Hi are you ceonnected on the power adapter? To be able do run the mac on an LCD with the LId closed make sure the laptop is connecetd on the Power Adpater

I'm sure most if not all of us are. This is an issue that just popped up after 10.8.2.

In any case, Macs won't even wake with the lid closed without AC and display plugged in. In this situation the Mac will wake, the display will show the login screen, then about 10 seconds later the Mac seems to ignore that screen, realize the lid is closed, and go back to sleep.

Nothing in Console seems to show what's deciding that anyway so we don't have much to start with...

Found something that seems to sort mine. Reset the NVRAM (http://support.apple.com/kb/HT1379) and try the sudo command again in Terminal and reboot.

Mine's now back to normal, the 10.8.2 update did mention something about a firmware update so I suspect that's what's knocked it off.

Doesn't seem to have worked for me... 😟

It also seems to have worked for me. The steps for anyone so you can it them a try:

• Reset NVRAM (restart, hold "Command", "Option", "P", "R" keys from start, then wait until you see the grey boot up screen for just few secs until you see it restart again).
• Enter in the Terminal the famous > sudo nvram boot-args="iog=0x0"
• Shutdown/Reboot the system

I've got it working now, built-in screen off, external monitor on with lip open. I have not yet tried to put it to sleep and back on again... don't want to push my luck.

This worked for me (Retina MacBook Pro):

- Reset NVRAM

- Booting into startup disc selection (or whatever its called - press option key on start-up)

- Select to restore your system (if the option is not available reinstall M-Lion it via USB stick)

I'm still on 10.8.2 but Thunderbold and HDMI work as before with external screens.

Some gotchas that I had to take care of:

- Disabled FileVault

- Resetted SMC

- Repaired Disc and restored Permissions

- Did a System Diagnostig (hold d on startup)

I have been using clamshell mode with my Mid 2009 MacBook Pro (MacBookPro5,3) with the same monitor all the way from Snow Leopard to Lion to Mountain Lion. Now when trying to use clamshell mode, closing the lid, hooking up my monitor, keyboard and mouse, does no longer wake up my Mac from sleep. This has happened after upgrading to 10.8.2. The monitor turns on, but turns of after 5 seconds and my Mac goes back to sleep again. None of the mentioned fixes works for me. Please fix this problem Apple.

Same here thomnas. I'm running on an older 2007 MacBookPro3,1. Apple please fix this defect in 10.8.2.

Apple, please _restore_ this fundamental functionality that is making my monitor useless, my desk setup a joke and all the rest of it? Why break things with a "software update"? Bad quality checks on your releases!

Same problem here.

Apple, please _restore_ this fundamental functionality that is making my monitor useless [2]

That is a fu&ˆ@#ˆ*&@ shame!

I'm really tired of this problem. I can't use my external display and I can't use ANY external projector!