end point curve joining problem

Hey guys, when I try to join two  continuous curves together it looks visually good but but when  I try to perform curve operations on it.. like get a mid point, it explodes it again into 2.. is there a way to 'weld' this connection point so that rhino sees is as a true curve and not a curve made of 2 joined pieces? again, its continuous.. even on a line it still does it.