Dual monitor login issue!

Same problem here after update to Yosemite. Interesting twist here...at least I haven't seen it mentioned yet, but mouse behavior is reversed as well. The outside edges of each monitor are the transition edges. Kinda trippy, but a fix would be nice!

On July 9, 2015, I'm having a similar problem after migrating from 10.7.5 to Yosemite 10.10.4

That is, I have a main Cinema Display on the left which has always had the login screen so I could chose one or the other of my user accounts.

My second monitor (Viewsonic) on a second video card in the MacPro workstation) extends my desktop to my right.

Now, After Yosemite installation, the login window appears on the right whether or not the monitor is turned off (either visible there or simply invisible "off-screen").

Also very troubling, after this login window appears on the ('wrong') monitor to my right, the logitech bluetooth mouse is (initially) active ONLY on the Cinema Display Main monitor to my left, and (initially) I cannot move the mouse to the extended region on the Viewsonic monitor where the login window is.

After a ?minute or so the OS seems to sense my panic and a bit of apple anger and responds by finally allowing me to get 'through the locked wall.

(Posit;y related in my case -->There used to be an ability in some preference to conditionally "lockScreen", as I recall, but I can't find that.)

NOTE--> So, What I want is a way to change the location of the "startUp Login Window" from the extended Viewsonic display to the Main Cinema display on the left.

Is there a key combination to force that ?

Do I have to completely disconnect my view sonic extended monitor from my second video card and then restart ?

Would that fix work and persist as I'd like it to ?

(Note I have folders of course over the extended desktop on both monitors.)

I have the same problem. I just upgraded to Yosemite, and now I am unable to have the startup login appear on the primary monitor (which is my Thunderbolt display). All other functions are normal, but I have to log in from the monitor that is the computer (this is an IMac). Before the upgrade, ALL functions, including the login screen, were on the second monitor - l liked it that way. Now I am forced to log in from the IMac screen, and then once logged in, the Thunderbolt is primary, and the IMac screen secondary. This problem seems to be an oversight in Yosemite as the problem only appeared after the upgrade.

I have two Thunderbolt displays and had the same problem, in El Capitan actually. Since each user sets his own Display arrangement I wondered where the Display arrangement would be set for the Login window. I tried to login to the Admin "root" account via the GUI. It froze up. It always worked before. I disabled and reenabled the root login. At some point the login Display changed back to the correct display. It seemed like disabling and reenabling the root user fixed the problem. This may not be the case, but it is worth a try. Especially if you have the root user enabled. After disabling and reenabling the root user I was able to log in again with the GUI. So at least that is working now, I rarely, if ever, have a reason to log in that way. I have root enabled mostly because I get tired of typing sudo, if I am doing a bunch of things.

I had swapped my Displays because of trying to troubleshoot another (USB Thunderbolt) problem.

I hope this potential answer is helpful to someone out there...

Hi markfromlandolakes - thanks a lot for this tip, which helped me solve the problem.

I have two screens, a main one and the other is the video projector, and for a few weeks the login screen always showed on the projector, even when it is switched off. And no manipulation (using mirror screens, changing order, the place of the menu bar, etc..) could solve the issue.

Activating the root user, then login (actually the first login with root led to a black screen for which I had no other choice than use cmd-ctrl-power to restart - the next one worked OK), then set up the screens correctly (menu bar on the correct screen), and after logout the login screen no longer is on the video projector. It seems to have survived deactivating the root user and a reboot, so I hope it stays like that...

That's really a stupid OS X bug - the login screen should just follow where the mouse pointer is, it's simple enough...

Hi,

I was having a similar issue. I have a Macbook Pro with the retina display and an external monitor (HP LP2475w). I usually use both displays and login on the external monitor. Today my external monitor would not light up until after I logged in. My issue started and will continue because I turned on File Vault. Apparently File Vault doesn't allow access to any peripherals until one logs in. Choices are, turn File Vault off or live with logging in on the Macbook display. For now I'll just login on the Macbook. Hope this helps someone.

My login screen is different from my Primary Monitor as well which is not the case before Yosemite, very annoying.

Hopefully, Apple would fix it soon.

OS X update 10.10.1 appears to fix the issue today.

Thanks for the update.

Well. It only worked after the update restart but not after a shut down.

Thanks for the attempt to solve my dual monitor issue, unfortunately it did not have any effects for me. Thanks again.

Same problem with me (and even if my external monitor is turned off)

I have to unplug/plug my HDMI cable to get the main screen back on my laptop.