Q: Mac Pro keeps logging out since El Capitan

This is happening to me also. I'm also on a early 2009 Mac Pro. Like you I'm randomly logged off.

I am also having his same issue.  I haven't been able to isolate the cause of logging out.  I think it is triggered by user input, but I'm not certain as of yet.

I also have an Early 2009 Mac Pro.  I did not have a kernal panic post-install.

This is happening to me also. I'm also on a early 2009 Mac Pro. Like you I'm randomly logged off.

Update: Thank God for Carbon Copy Cloner. Back to Yosemite and everything is fine again. Won't be attempting upgrade to El  Capitan again any time soon.

I have the same problem with my MAC PRO 2009. I reinstalled software twice and removed all of my startup aps. then I pulled the 2 USB3 cards I added 1 year ago. Still had the same problem. As a last resort I unplugged my 2nd viewsonic monitor and the trouble stopped. I reinstalled my USB3 cards still no trouble. I plugged back in the 2nd monitor and problem is back. Apple programmers seem to have a problem with duel monitor operation. They screwed me up once before by not supporting 2 monitors from 2 cards. Just lazy programming if you ask me.

I don't know if anyone is running 2 monitors out there but unplugging the second one may help.

Yes, same issue.  Mac Pro early 2009 and El Capitan and it keeps logging me out.  Not good at all.  I am also receiving OpenGL errors in the log.  This is poor.

Brian

We have the same scenario.  I'm using a 2 monitor setup with 2 video cards.  When I get home from work I will test out removing my second monitor and see if the problem resolves.

Yes, same issue.  Mac Pro early 2009 and El Capitan and it keeps logging me out.  Not good at all.  I am also receiving OpenGL errors in the log. 

I also have 2 monitors and 2 GT120 cards in my system.  I can confirm that unplugging the second monitor makes the system work normally. 

Brian

All of our coders use Early 2009 Mac Pro's with multiple monitors- we "fixed" this logout issue by reducing them down to one monitor- but that is unacceptable-- This is an obvious bug- El Capitan was supposed to be the great "stable" release of yore.

I have same problem on my 2009 MP. Only using the GT 120 resolves that problem.

However, I can't screen share or file share into the 2009 with 10.11. I can screen share if I ask for permission but after 5 minutes or so I lose the connection.

I am screen sharing fro a 2013 Mac Pro with Yosemite

I know this is a horrible fix (Apple should get this bug fixed via code) but I managed to fix my personal dev box (early 2009) by swapping out my 2 - GT120's for a single ATI HD6870.  My guys on the other hand are still struggling with a single monitor- *****!

The GT 120 support two monitors that is what I am now using.

Right- I know the GT 120 should support two monitors- it seems as if the GT120's are the problem-  The AMD [ATI] HD6870 video card is cruising along right now with three monitors attached without a single logout.

Same issue for me:

Mac Pro 4.1, early 2009, quad core 2.66ghz

16GB Ram

512GB SSD

2 x Nvidia GeForce GT 120 video cards

3 x Apple Cinema Display 23" monitors

Since upgrading to El Capitan this morning, my system crashes constantly. By constantly, I mean every few seconds. Sometimes the system just goes to sleep; other times it locks up an the screen goes funny; other times it completely shuts down. The cause seems to be the multiple monitors. It runs fine with only one monitor. But two or more and it crashes. The crashes seem to occur when I switch between application windows on different monitors.

I have updated the Nvidia drivers to the latest release.

Any help gratefully received.

Mac Pro (Early 2009), OS X El Capitan (10.11)