I have a Thinkpad W520 with Nvidia Optimus graphics. I have disabled the Nvidia card in BIOS (by selecting "integrated graphics"), so I'm running only on the integrated Intel graphics. I get full 3D acceleration, which would suggest the drivers are properly installed. However, I'm not able to use an external monitor. With the external monitor connected and turned on, running xrandr always gives:

$ xrandr
Screen 0: minimum 320 x 200, current 1920 x 1080, maximum 8192 x 8192
LVDS1 connected 1920x1080+0+0 (normal left inverted right x axis y axis) 344mm x 193mm
   1920x1080      60.0*+   59.9     50.0  
   1680x1050      60.0     59.9  
   1600x1024      60.2  
   1400x1050      60.0  
   1280x1024      60.0  
   1440x900       59.9  
   1280x960       60.0  
   1360x768       59.8     60.0  
   1152x864       60.0  
   1024x768       60.0  
   800x600        60.3     56.2  
   640x480        59.9  
VGA1 disconnected (normal left inverted right x axis y axis)

What gives? It sees the VGA1 port (to which the external display is connected), but it appears disconnected.

I have tried forcing a resolution as per these instructions, but when I do that X becomes unresponsive and I have to Ctrl-Alt-F1 and restart it.