When making a selection of multiple anything by window, after the selected items are highlighted by civil.... you are misteriously and without notification Switched focus! Civil 3d is no longer the current program Running! You have to click on the Task bar and then click again in the civil 3d window to be active in civil 3d again. Then you can proceed as normal. Until you select by window again, and then you have to do the Click outside civil and click inside civil. It's as if Civil 3D loses focus when you select multiple items.
Yes it happens if nothing else is running and my civil 3d windows is maximized. I don't really know what is going on, but loosing focus is the best way to describe it. It is as if the computer switches to another program but the display doesn't change other than my crosshairs become a standard pointer.