Have you checked your router/firewall logs and disconcertingly see connections to an unknown IP207.246.119.209:3478 from your Grandstream VOIPphones?
You're not alone and the Grandstream forums have discussed this issue.
However, even their own staff d........
It may appear to be an Xorg or lightdm/gdm/mdm error but in reality for many users with this issue, it's a driver conflict and issue. I had a system that had two GPUs, an Intel and Nvidia GPU.
The only thing that got it working was to remove the nouveau driver and blacklist it so it never came back, then the Intel GPU works fine without these issues.
Solution
sudo rmmod nouveau
add nouveau/other driver to blacklist
edit th........
The display manager is more so what controls the main graphical login process after Debian/Mint/Ubuntu boot and controls the graphical login sequence. Once you login, you are then usually passed to an Xorg based Window manager like XFCE, Mate, Ubuntu etc...
Popular display managers are mdm, gdm, lightdm etc... and they all basically do the same thing with a different interface/style and some feature differences.
In Mint for example the normal default display manager is l........
This is not the normal "black screen"issue and I was shocked to eventually find out why. The normal advice of reconfiguring Xorg didn't work. Even booting into "Recovery Mode" did not help.
Here is the short end of the stick that fixed it:
sudo apt-get install mdm mate-desktop-environment
Yes you got it right, mdm and the mate-desktop-environment / gnome were somehow uninstalled. This must be whe........
I've never understood how to enable and disable services for different run levels in Debian based distros, it's just weird, annoying and doesn't make sense. I much prefer chkconfig from RHEL.
Just install the package called 'rcconf' and be done with it. rcconf makes things easy for you.
apt-get install rcconf
Reading package lists... Done
Building dependency tree
Reading state information... Done........
I decided on using yum to help me decide even though I normaly use proftpd I decided to see what else I could find.
yum search ftp
Loaded plugins: fastestmirror
Loading mirror speeds from cached hostfile
* rpmforge: ftp-stud.fht-esslingen.de
* base: mirrors.netdna.com
* updates: updates.interworx.info
* addons: yum.singlehop.com
* extras: mirrors.netdna.com
rpmforge........