Cone can't be drawn for duplicated lamps, because lamps with cone are drawn after main draw function (from view3d_draw_transp) and list of duplicated object gets freed to this moment. Disable cone draw for lamps which are from dupli.
Cone can't be drawn for duplicated lamps, because lamps with cone are drawn after main draw function (from view3d_draw_transp) and list of duplicated object gets freed to this moment. Disable cone draw for lamps which are from dupli.