Black screen after plymouth[xorg-edgers]

[fcole90]

After the plymouth animation the screen stays black when using nvidia drivers on my GTX850M with optimus.

Some time ago they worked correctly, since then I made two changes:
- switched to the Vivid stack for 14.04 from the utopic one;
- switched from mamarley/nvidia ppa to the "blessed" graphic-drivers ppa

If you need more information, I'm available to help.

[fcole90 (fcole90)]

I've purged all the nvidia-packages and tried reinstalling again and rebooting.
At the first time the boot reached plymouth and then rebooted.
The second time it went after plymouth and tried to load lightdm but failed gracefully to the graphics troubleshoot dialog. Once there I moved to tty2 and logged succesfully. prime-select query returned nvidia. I was able to prime-select intel so I tried starting lightdm with intel, but that triggered and endless lightdm boot loop, I could not see anything but I was repeatedly hearing the sound that lightdm does when strts. Also, the screen was always black but in each loop it went like on and off (with on I mean turned on but still black).

[fcole90 (fcole90)]

If you need any other file or test, please, tell me.