Lenovo X230 i7, HD4000;
Have the same problem on latest drivers (release and beta too).
Displayport on laptop and DVI port on dock station doesnt work. Graphic card cant detect displays connected via this interfaces.
Ubuntu 14.04 works fine on similar situation on this computer.
I found that when i install or uninstall drivers computer switches to the external monitor once. After reboot it does not work;
Monitor show that cable is connected properly, but there is no data. If i unplug cable monitor says "No connection".
I thing it is driver issue.