Duplicate Clip

1 
function thumbnails_fn_r(kr) {
    r_menu.createEmptyMovieClip("t"+kr, r_menu.getNextHighestDepth());
    tlistener_r = new Object();
    tlistener_r.onLoadInit = function(target_mc_r) {
        if ((kr%2)!=0) {
        target_mc_r._y = hit_top._y+(128-60)*(kr-1);
        target_mc_r._x = 140;
        } else {
            target_mc_r._y = hit_top._y+(128-60)*kr;
        }
        target_mc_r._xscale = target_mc_r._yscale = 50;
        target_mc_r.pictureValue_r = kr;
        
        target_mc_r.onRollOver = function() {
            //trace(this);
            this._alpha = 50;
            //if (_root.flagPress == 0)
            thumbNailScroller_r();
        };
        target_mc_r.onRollOut = function() {
            this._alpha = 100;
        };
        
        [COLOR=Blue]target_mc_r.onPress = processPressClip;[/COLOR]
    };
    image_mcl_r = new MovieClipLoader();
    image_mcl_r.addListener(tlistener_r);
    image_mcl_r.loadClip(thumbnails_r[kr], "r_menu.t"+kr);
}

var currentTarget:MovieClip;

function dup(m_mc:MovieClip)
{ 
[COLOR=Blue]trace(m_mc); // _level0.r_menu.t0[/COLOR]
    var nextDepth:Number = r_menu.getNextHighestDepth();
    m_mc.duplicateMovieClip("f_mc"+nextDepth, nextDepth);
    
    var duppedClip:MovieClip = r_menu["f_mc"+nextDepth];
    [COLOR=Blue]trace(duppedClip); //undefined[/COLOR]
    currentTarget = duppedClip;
    
    duppedClip.onPress = processPressClip;
    duppedClip.onRelease = processReleaseClip;
    
    duppedClip.startDrag();
}

this.onMouseUp = function()
{
    if(currentTarget != null){
    removeMovieClip(currentTarget);
    currentTarget.stopDrag();}
    currentTarget = null;
}

function processReleaseClip()
{
    this.stopDrag();    
}

function processPressClip()
{
    [COLOR=Blue]trace(this); //_level0.r_menu.t0[/COLOR]
    this._parent._parent.dup(this);
}

why movieClip is not duplicating?