Cross posted from serverfault:

I'm having the weirdest issue. We use SL7.2 and have a network home 
directory and AD + SSSD for auth. This means I can go to different 
computers and get a consistent home dir as well as UID/GID etc. I have a 
physical KVM to set up computers more easily.

I started having an issue where my workstation would stop displaying X 
to my monitor. The monitor will say "No Signal" It would work fine until 
I switched away via the KVM to another computer, when I switched back X 
would not display. I could connect via Bomgar and see my X session, it 
was fine. I could ctrl-alt-F3 and the virtual terminal would display, 
but the only way to get X back was to reboot.

I thought it might be the KVM, so I connected the monitor via DVI 
directly to the workstation. No change.

I thought it was an issue with the hardware or the OS install, so I set 
up a brand new Lenovo P510 with a new SL7.2 install. Now it will loose X 
if I just don't use it for a while (I think it's the screen locking?).

I thought it might be the monitor - maybe it's old and loosing signal, 
or the new Display port to DVI adapter can be funky, so I installed a 
brand new BENQ GW2765, connected directly via Display Port to the nVidia 
card (this card only has Display Port connectors - 4x). No change.

However, this last time Bomgar could not show the X session...

So now I'm thinking - it HAS to be software, and it has to be something 
in my configuration. But I don't really even know where to start looking 
- /var/log/messages and /var/log/Xorg.0.log don't show anything that's 
obvious to me.

How can I fix X not coming back?

-- 
James Pulver
CLASSE Computer Group
Cornell University