Comment 33 for bug 873495

@Carl: so this has probably very little to do with the nvidia driver itself if you can reproduce it with intel.

I think I need more information to understand where the problem lies (lightdm could probably run some checks before starting X).

Can you reproduce the problem and attach the content of the following directory, please? (you might need root privileges)

/var/log/lightdm

You can do something like the following:

1) reproduce the problem
2) type this from the command line:
sudo cp -a /var/log/lightdm ~/
3) tar the directory and attach the resulting file.