I did as Alberto said, and nothing has changed. For the sake of purity I have creted a new user and tried to log in. In this case X just restarts, I am attaching a log file with the crash backtrace in the end.
** Attachment added: "Xorg.0.log.old" https://bugs.launchpad.net/ubuntu/+source/xorg/+bug/1236996/+attachment/3868745/+files/Xorg.0.log.old -- You received this bug notification because you are a member of Ubuntu-X, which is subscribed to xorg in Ubuntu. https://bugs.launchpad.net/bugs/1236996 Title: Nvidia Optimus laptop shows black screen with mouse after sucessful login To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/xorg/+bug/1236996/+subscriptions _______________________________________________ Mailing list: https://launchpad.net/~ubuntu-x-swat Post to : ubuntu-x-swat@lists.launchpad.net Unsubscribe : https://launchpad.net/~ubuntu-x-swat More help : https://help.launchpad.net/ListHelp