December 16, 2011, 01:39:25 am
I think using the C key is just coincidence when you click to place them somewhere. It's the Ctrl key plus click that does the duplication.
So when you go Ctrl +C and then click somewhere it's the click that is finalising the action and the C is not really being recognised.
See FAQ "Place object mode -> (CTRL) + Left-click: Randomly place 10 copies of the currently active object library model."