Thank you for the updated information. The end of your Xorg.0.log shows that the xserver is crashing. For that we would need a back trace in order to figure out what causes it. Take a look at https://wiki.ubuntu.com/X/Backtracing for how to do that. It's probably easiest with apport. That may generate a new bug report, but that's okay. Just link to it from here.
Thank you for the updated information. The end of your Xorg.0.log shows that the xserver is crashing. For that we would need a back trace in order to figure out what causes it. Take a look at https:/ /wiki.ubuntu. com/X/Backtraci ng for how to do that. It's probably easiest with apport. That may generate a new bug report, but that's okay. Just link to it from here.