Dell XPS 17 on 14.04 using Nvidia drivers, was working fine, but now only shows output on the screen connected via HDMI connection, and not the laptop screen. There's output on the laptop screen when its booting etc, so I know it still works ok, but neither the 'Settings > Display' tool, Nvidia-settings, or xrandr detects the laptop screen anymore.
eg
buddha:~> xrandr
Screen 0: minimum 8 x 8, current 1920 x 1080, maximum 16384 x 16384
HDMI-0 connected primary 1920x1080+0+0 (normal left inverted right x axis y axis) 598mm x 337mm
1920x1080 60.0*+ 59.9 50.0 60.1 60.0 50.0
1680x1050 60.0
1600x900 60.0
1440x900 59.9
1400x1050 60.0
1280x1024 75.0 60.0
1280x800 59.8
1280x720 60.0 59.9 50.0
1152x864 75.0
1024x768 75.0 60.0
800x600 75.0 60.3
720x576 50.0
720x480 59.9
640x480 75.0 59.9 59.9
Any way to 'reset' this so that it detects the inbuilt screen again?