Just to follow-up quickly, it appears to be "driving" a "No Monitor". I can seem to change resolution, to move windows on and off, change their size, unplug the monitor and have every "flash" -- I can basically do everything but make the monitor display anything.
The monitor that's not behaving is a ViewSonic VX2450wm.
Image of what I see in the control panel:
The one on the right, #3, is the "No Monitor". The other two have outputs.