random crashes to login screen after updating to Yosemite

[b.c.]

since upgrading my iMac to Yosemite last week, twice now I've seen this happen:

With a couple users are logged in on this Mac using fast-user switching, each with an application or two left running (e.g. Safari, iTunes, etc) ... on random occasions, immediately after logging back into one user, the whole screen momentarily goes black (cursor still visible, though), then I get dumped out to the login screen and both users are now logged out. No other particular user action was happening at the time - just re-logging in waiting for the desktop and app windows to all reappear, then... poof

it's like the computer is crashing, except instead of fully rebooting, all users' applications are closed and logged out. I've never seen this happen before in OS 10.9 or prior, on this or any other Mac I've used

anyone else seen this happen after updating?

iMac 27inch late-2009, 2.8GHz Core i7, 12GB RAM
running Mac OS X 10.10

 

[b.c.]

I'm still having this problem...

every once in a while, moments after I log back into my user via fast user switching, the screen momentarily goes all black, then suddenly back to the login screen with all users logged out.

Like a crash, but the machine itself doesn't crash - just all apps and finder "crash" dumping everything out to the login window. Today it happened without me actually re-logging in back first. i.e. using fast user switching menu, I went to the login screen leaving my user and apps running. Less than an hour or so later I came back to my Mac and found the login screen there, but all users logged out.

anybody else see this?

also, is there an easy way in the console logs to find the trigger, e.g. next time I witness what time it happens?

 

[marlun]

I'm having the same problem. Every now and then OS X just logout and when I login all the applications is restared. I can pretty much be doing anything when it happens. A couple of minutes ago I was just starring at the screen thinking when from nowhere I get logged out.

I'm on OS X Yosemite 10.10.1 and MacBook Pro (15-inch, Mid 2010)

 

[Weaselboy]

It sounds like you may have a login or startup item that conflicts with Yosemite. Try holding the shift key to boot to safe mode and see if the issue goes away. Safe mode bypasses all login and startup items as a troubleshooting tool.

If that fixes it, use the tool Etrecheck to see a list of all startup and login items so you can start removing them to find the culprit.