This is not the same as this question.
I have Ubuntu 12.04 running with an Nvidia card on a W510 Thinkpad. I have one external monitor connected. When I change the power settings to "Do nothing" when "Lid closed" it still keeps the system running which is great. However, it blanks out the display on any external monitors making the system useless. I plan on getting a dock soon and having to identical resolution monitors and would love to be able to dock the monitor and work as normal on the external monitors. Does anyone have a suggestion or fix for this? Should I report this as a bug or feature request?