My Lenovo X200 laptop has developed a problem recently whereby I get a blank internal screen on booting into Ubuntu 11.10 (display works normally during boot and I get a moment of desktop before it blanks out. gnome-shell menus are not visible during this brief flicker of desktop).
It seems that my laptop 'thinks' an external monitor is connected (and is set as the primary monitor, without mirroring or extending to the internal display), even when there's no monitor connected. Here are some observations:
If I connect to an external monitor, then my desktop appears on the external.
I can then successfully use displays (system settings) and xrandr to turn on the internal display (which is set to 'off'), and can then mirror or extend across both displays.
Once I've turned on the laptop screen and set it as primary, I can disconnect the external monitor and use the laptop display independently.
If I fire up the laptop without an external display (in which case I get the blank screen), I can switch to an alternative terminal, e.g. tty1, at which point my internal display functions correctly, but if I return to tty7 it blanks out again, and at this stage I can no longer switch to tty1, tty2, etc.
I can boot into Windows no probs.
If I cast my mind back, I think it's quite possible that I meddled with some settings somewhere in the past in order to set the external monitor as the primary display when the laptop was docked, in which case I wonder if someone might direct me to potential files that I might have modified (and remind me of the changes that I may have made), so that I can revert to the original settings. This would have been a while back though, I think, in Maverick or Natty (and I don't know whether such modifications would persist on upgrade). This is a recent development, though, so I think there's more to it than that.
I can't think of any software installation or changes to system files that might coincide with the problem appearing.
Does anyone have any ideas for how to diagnose what's wrong here? Much appreciated. If there's a command I can use to print out relevant system info, please let me know and I'll update the question with the details.