I had this same thing occur on my main desktop computer as well. Knowing that the xorg.conf file got trounced on my main notebook, I made sure I had a good backup of my xorg.conf file before beginning the LTS upgrade.
At the conclusion of the upgrade, the xorg.conf file was still in the directory. Upon IPL, however, it was gone, and X started without the correct settings. I copied from my backup, IPL, and Xubuntu came up with the correct display settings.
This desktop system transitioned up to driver package: nvidia-331 during the LTS upgrade. On this system I had already selected: nvidia-current-updates ... not sure if the notebook had the "-updates" version of the package, might have simply been "current" on that system.
I had this same thing occur on my main desktop computer as well. Knowing that the xorg.conf file got trounced on my main notebook, I made sure I had a good backup of my xorg.conf file before beginning the LTS upgrade.
At the conclusion of the upgrade, the xorg.conf file was still in the directory. Upon IPL, however, it was gone, and X started without the correct settings. I copied from my backup, IPL, and Xubuntu came up with the correct display settings.
This desktop system transitioned up to driver package: nvidia-331 during the LTS upgrade. On this system I had already selected: nvidia- current- updates ... not sure if the notebook had the "-updates" version of the package, might have simply been "current" on that system.