OS X Yosemite Keeps Crashing To Log-In Screen

I have the same issue but mine reoccurs every day, at the end of the day. I mean literally every day. I have been dealing with the issue ever since doing the beta as well. I have been working with Senior Tech advisers with Apple and no one can figure out the issue. I have literally done every test you can think of. I also went in to the genius bar to see if they could figure it out as the tech suggested. Apparently Apple engineers do not know what is causing it either. I sent over a data log and never heard back. Never heard back from the guy at the genius bar either. He said lets wipe your comp and then dont put anything back on it.... and I'll get with you to finalize. No call, no email, no contact. Pretty unimpressed with Apples customer service with this issue as they have left me with a computer that no longer functions correctly.

Brand-new iMac with 5K Retina, here. Regularly having WindowServer crash, dropping me back to the login window and losing everything in all running applications.

I have two external monitors, one connected to each Thunderbolt port.

Most of my crashes occur when logging in or logging out of different user accounts. (This Mac has two frequently used user accounts.)

I've also noticed that the Cursor Size feature of accessibility has some real issues with multiple users like this. Not sure if it might be related or not. There are a couple threads out there about this. Here's one: Cursor Problem

Interesting post about the cursor and the multiple monitors. The multiple monitors has turned up before and questions raised about the graphics driver.

I have two machines

- One laptop with no external monitor - Never a fault.

- One 27 inch iMac with external thunderbolt monitor - Regular fault even after re-install.

On the iMac I changed the cursor size due to the large real estate. (Both installs)

Has anyone else re-sized the cursor?

Always had standard size for the cursor.

Uptime with the Beta update is 13 days now, spent a lot of that time rendering/video editing. Didn't have a single crash and im pretty much back to normal usage, so... i think its fixed with 10.10.2, whatever the reason was. Maybe someone else can comfirm this, could be that im just lucky i guess? In any case, the beta is free to try after installing a little helper tool and since everything seems to run fine id recommend to just give it a try:

https://appleseed.apple.com/sp/betaprogram/redemption

I don't have Omni installed. The only common apps that I use that I've noticed this occurring constantly with are Chrome and Messages

I, too, have seen a huge improvement in 10.10.2 Beta. It is 99% more stable, but I have had a couple of failed/locked issues. Can't pin them down to a logical reason yet, but working on that. One morning I awoke to a login screen reset, but haven't had one in a few days now. Still something not right, but that could be something I installed, or a non-compatible app that needs an update.

I'm not convinced it is entirely fixed, but this might stop me from having to go back to Mavericks, if it holds up. I have worked to create a Mavericks install USB drive and have backed up everything I want to keep, so I am just waiting for another reset/reboot, then I will pull the trigger and wipe out Yosemite on my iMac.

Apple has really dragged their feet on this one. I can only guess from the delay of the third beta, they are still getting problem reports. I figure we are looking at another beta release before all the issues are fixed.

Flashback: This Yosemite release reminds me of the days of the Apple III. :-)

Can I assume you are a recent Windoze convert-to-Mac? Why? If you are happy using Windows applications, what is the reason you are using OS X? Not being snobbish, just curious?

Everything written on the blog link above says every thing about what was Apple, and what is today!

http://www.marco.org/2015/01/04/apple-lost-functional-high-ground

They need to stop, and and clean there OS X...

Both my Yosemite systems are doing this. The MBP and iMac. Twice a day --- very very annoying especially when one is in the middle of complex work!

Disconnecting monitor is common for me.

Just 5 minutes ago it was starting numbers!

Not repeatable, numbers started OK.

I can confirm that upgrading to the 10.10.2 beta fixed this.

It broke other things though, but at least this now works!

Same. 10.10.2 beta fixed the issue for me.

I've been having this problem too, ever since updating to Yosemite. Currently running 10.10.1 on an iMac 27" late 2009, 2.8GHz i7, 12GB. Unlike some others here, I'm not running a secondary display.

problem occurs randomly, but frequently enough to be annoying (often once or twice every day) usually when switching users via Fast User Switching - instead of keeping my user and applications active, it kills all the apps and processes and dumps out to the login window with my user logged out. Typically I might have a couple applications left running, iTunes, Safari, perhaps Excel. On occasion, I've seen it do the same when logging back INTO my user account via fast user switching - the screen will momentarily go blank and dump back out to the login window, quitting all apps and logging out in the process.

I've been noting the date/time whenever I witness it happen and have been poking around the console logs for clues. I do see WindowServer crash logs at corresponding times in the System Diagnostic Reports section of the console logs, although I'm not sure how to decipher...

I have been on this forum now for a month or two and have read most of the complaints and comments from lots of disgruntled, Apple users. I was hit with the reboot and panic problems after installing Yosemite 10.10.1. I did not have this problem on the initial install of Yosemite. I have tried and tried and tried just about every fix or trick suggested on this forum, and uninstalled apps, reinstalled Yosemite, and nothing fixed my problem until today.

I have never noticed any problems with wifi. They may have been there, but they were not as intrusive and annoying as being logged off, or have my Mac reboot for no earthly reason. Today, I could not even stay logged in for more than a few seconds before a reboot or panic. I could not understand why this was so erratic over time?

I shut down iCloud Drive. This stopped the "bird" process from eating 99% of my CPU. I have been using my Mac all day and everything is a solid as before Yosemite. that is all I did, and miraculously it stopped rebooting and freezing up.

I would be very interested in others responses to this proposed fix.

I never turned on iCloud Drive on any of my OSX or iOS devices. So this will not be the only cause of this problem, but I hope it would solve this problem for you.

Well, I was overly optimistic. I didn't have any panics all day yesterday, but this morning it hit again. It appears shutting down iCloud sync helped a lot, but didn't solve all of the problem. There must be multiple issues triggering each other, or something. This is really frustrating?

I have run advanced diagnostics to try to find any hardware issues, but there are none reported. I have a Macbook Pro (Mid 2010) that is running the same OS and it has never rebooted on it's own since Yosemite upgrade back in October 2014? I have no idea why my iMac (2012) is having panics all of the time. I can use it for a few minutes, or sometimes an hour, before it reboots, with no indication of the cause? I am not convinced it isn't a non-reported hardware problem, but I have ran the diagnostics several times and it never reports any errors. It is useless at this time. I'm using my MacBook until someone has a definite answer to the random reboots and panics in Yosemite for iMacs.