Q: Mountain Lion keeps logging user out...

Lion with Spaces and 1 montior is better then Lion without Spaces and 2 monitors.  I use the spaces for task work.  But, I can see if you were working for long periods of time in Photoshop, FCP or some other app, you might prefer no spaces and dual monitors.

I unplugged one of my monitors also on my MDP Early 2009 with 2 NVIDIA cards and no logouts.   Didn't pull the card, just unplugged the display while running.

Two+ monitors isn't the issue. Neither is two graphics cards. Neither is Spaces.

The problem is very specifically having however many monitors plugged into MULTIPLE graphics cards.

I haven't removed a single card from my system, I simply used both of the ports on one of my graphics cards (what good graphics card nowadays doesn't have at least 2 ports of some sort?) and the issue went away.

I'm sure it's just a catch in the OS somewhere when it's trying to decide which card to use - Apple just needs to remedy the situation already.

But, if your graphics card has two ports - use them and have your multiple monitors and don't be afraid of Spaces. It all works great. Just as long as your monitors are only using one graphics card

Having the same problem. I'm in the same boat with quad core MacPro, duel grahics cards, and three monitors. I Started another thread here. I didn't see this one intialy. I will ref this thread as well. I did call to report the issue to Apple, and they suggested a clean install. That would be a hassel and it seems that it won't work either.

https://discussions.apple.com/message/19126239#19126239

I think you are right, two graphics cards, multiple monitors.  May not have anything to do with Spaces necessarily.  Could be just regular ole OS to graphics memory management and backing stores. 

I think many of us with the problem did not buy the systems or the cards "nowadays".  At least my cards were purchased some 2.5+ years ago.  My NVIDIA cards support single monitor.   And, for some of the people that are doing intense video and graphics, they needed the additional card performance to support the rendering and imaging that two graphic cards support.

I think you can tell that that a good handful of people have tried a clean install, and that did not solve the problem.  I can easily think I heard of no less then 5 have tried that and that is with NVIDIA and ATI cards.

Clean install is obviously not the issue.  All Apple will need to do is read this thread and it's obvious the issue is multiple graphics cards, with monitors plugged into each.

To sumarize for new viewers...

If your system has multple cards, and monitors plugged into more than one card...

• Systems with cards that allow multiple montiors - plug monitors into single graphics card (no need to remove other card).  If you have two Apple Displays that require Mini Display Ports, your card will need to have two ports. For older cards such as GeForce GT120 (which only has one Display port, and one Dual Link DV.. you'll need to use monitors that support this, or go with a single monitor.)
  
  
• Another solution here that I have not tested but seems to work.. go into Expose and delete all Desktops except one.  This will essentially keep the system from using Spaces.

I was fortunate enough to have an ATI 5770 at home which I could swap out at the office (swapped out two GT120s for the one 5770 giving me the ports I need on a single card).  This allowed me to connect my two Apple LED Cinema Displays and keep up my workflow..

It's not perfect, but hopefully it'll help keep us working until Apple addresses this...

This seems to be confirmed for me as well.

I've had one video card running two monitors for about 2 days, and the system has been very stable.

Will continue to run using a single video card until the next update (hopefully 10.8.1) fixes this.

-Jason-

Safemode seems to work great too:)

Guys,

This just started happening to me too. I have an MBP (2011) and just upgraded to ML. For me though it has nothing to do with multiple monitors as I don't have them......

For me, I unchecked "Disable automatic login" under Security & Privacy and all is good - strange hey??????

Q Manning

"Two+ monitors isn't the issue. Neither is two graphics cards. Neither is Spaces.

The problem is very specifically having however many monitors plugged into MULTIPLE graphics cards."

Please explain how you came to the conclusion that Spaces is not connected with this issue.

The facts in my case are: clean install, dual 120 cards, one monitor in each. For me the issue arises only when Spaces is enabled therefore Spaces is a factor (causal or coincident), the fact that you say this does problem does not occur when Spaces is used on multiple monitors via a single graphics card does not support your claim to exclude Spaces.

those having this problem should sumbit a bug report to apple.

bugreport.apple.com

Just for the heck of it, I tried the "Disable automatic login" and plugged my DVI monitor back in to the second card.  I now have two HDMI monitors coming off of one card from the mini-display ports and the DVI off of the other.  Did this almost four hours ago.  Not a single log out.

I don't use auto login on anything. I ran in safemode for a few hours yesterday without a random logout, but the desktop icon items disapeared, and there was some slowness. I also had to reconfigure the monitor layout and desktop backgrouds. For the record I'm useding 3 "spaces" and 3 monitors, with 2 nivida 120 grahics cards on a macpro 2.93 quad core.