Help with completing sentences game code

Question

Hi, I`m a bit stuck, I`m making a game where you have to complete the sentences by dragging the words which are generated dinamically to its right place over some boxes, everything works fine but if you pull the words out of the boxes one all are placed it crashes.
Unfortunately this is someone elses code (another programmer who bailed on us in the middle of the proyect) although I manage to make it work with new words, making the draggable items undraggable one you place all 4 of them in the right boxes is totally unclear to me. I`ll appreciate any help I can get.
Here`s all the code that this part of the movie is using:
function aleatorio(min, max)
    var _loc2 = true;
    if (usados.length <= max - min)
        while (_loc2 != false)
            var _loc1 = Math.floor(Math.random() * (max - min + 1));
            _loc2 = repetido(_loc1);
        } // end while
        usados.push(_loc1);
        return (_loc1);
    else
        return (0);
    } // end else if
} // End of the function
function repetido(num)
    var _loc1 = false;
    for (i = 0; i < usados.length; i++)
        if (num == usados[i])
            _loc1 = true;
        } // end if
    } // end of for
    return (_loc1);
} // End of the function
stop ();
var usados = new Array();
_root.palabras_colocadas = 0;
palabras_correctas = 0;
listado_x = 700;
listado_y = 400;
origenx = 0;
origeny = 0;
estaba_en = -1;
apagar = false;
_root.frase = 2;
var palabras = new Array("huts", "made", "mud", "straw");
var correctas = new Array(false, false, false, false);
var ocupadas = new Array(-1, -1, -1, -1);
var my_font = new TextFormat();
my_font.font = "Arial";
my_font.color = 0;
my_font.size = 30;
palabras[i].embedFonts = true;
my_font.bold = true;
var i = 0;
while (i < 4)
    this["cuadro" + i].gotoAndStop(1);
    this.createEmptyMovieClip("myClip" + i, this.getNextHighestDepth());
    largo = palabras[i].length * 22;
    this["myClip" + i].createTextField("label", 1, 0, 0, largo, 40);
    this["myClip" + i].label.text = palabras[i];
    this["myClip" + i].label.setTextFormat(my_font);
    this["myClip" + i].onPress = function ()
        temp = this._name;
        temp = Number(temp.charAt(6));
        if (ocupadas[0] == temp)
            apagar = true;
            estaba_en = 0;
        } // end if
        if (ocupadas[1] == temp)
            apagar = true;
            estaba_en = 1;
        } // end if
        if (ocupadas[2] == temp)
            apagar = true;
            estaba_en = 2;
        } // end if
        if (ocupadas[3] == temp)
            apagar = true;
            estaba_en = 3;
        } // end if
        if (!apagar)
            estaba_en = -1;
        } // end if
        origenx = this._x;
        origeny = this._y;
        trace ("estaba en " + estaba_en);
        this.startDrag();
    this["myClip" + i].onRelease = this["myClip" + i].onReleaseOutside = function ()
        this.stopDrag();
        cual = this._name;
        cual = Number(cual.charAt(6));
        drop = eval(this._droptarget);
        trace (drop);
        donde = String(drop);
        cuadro = donde.substr(8, 6);
        donde = Number(donde.charAt(14));
        trace (cual + " en " + donde + " " + cuadro);
        if (cuadro == "cuadro")
            if (ocupadas[donde] >= 0 && ocupadas[donde] <= 3 || donde == estaba_en)
                apagar = false;
                this._x = origenx;
                this._y = origeny;
            else
                if (!apagar)
                    ++_root.palabras_colocadas;
                } // end if
                tramo = eval("tramo" + (donde + 1) + "_mc");
                tramo.gotoAndPlay(2);
                if (_root.palabras_colocadas >= 4)
                    startbtn.start();
                    start_mc.gotoAndPlay(2);
                else
                    palabra_ok.start();
                } // end else if
                largo = palabras[cual].length * 8.500000E+000;
                drop.gotoAndStop(2);
                this._y = drop._y - 22;
                this._x = drop._x - largo;
                ocupadas[donde] = cual;
                if (apagar)
                    apaga = eval("cuadro" + estaba_en);
                    apaga.gotoAndStop(1);
                    tramo = eval("tramo" + (estaba_en + 1) + "_mc");
                    tramo.gotoAndPlay(6);
                    ocupadas[estaba_en] = -1;
                    correctas[estaba_en] = false;
                    apagar = false;
                    trace ("hay " + _root.palabras_colocadas + " palabras");
                    if (_root.palabras_colocadas == 3)
                        trace ("apaga sin ruido");
                        start_mc.gotoAndStop(1);
                    } // end if
                } // end if
                trace (ocupadas[0] + " " + ocupadas[1] + " " + ocupadas[2] + " " + ocupadas[3]);
                if (cual == donde)
                    ++palabras_correctas;
                    correctas[donde] = true;
                } // end if
            } // end if
        } // end else if
        if (cuadro == "myClip" || cuadro == "start_")
            palabra_error.start();
            this._x = origenx;
            this._y = origeny;
        } // end if
        if (cuadro == "fondo")
            if (apagar)
                apaga = eval("cuadro" + estaba_en);
                apaga.gotoAndStop(1);
                tramo = eval("tramo" + (estaba_en + 1) + "_mc");
                tramo.gotoAndPlay(6);
                ocupadas[estaba_en] = -1;
                correctas[estaba_en] = false;
                --_root.palabras_colocadas;
                apagar = false;
                trace ("hay " + _root.palabras_colocadas + " palabras");
                if (_root.palabras_colocadas == 3)
                    startbtn.start();
                    start_mc.gotoAndStop(1);
                } // end if
            } // end if
        } // end if
    ++i;
} // end while
var ii = 0;
while (ii < 4)
    var numeroNuevo = aleatorio(1, 4);
    trace (numeroNuevo);
    this["myClip" + numeroNuevo]._x = listado_x;
    this["myClip" + numeroNuevo]._y = listado_y + 40 * i;
    ++ii;
} // end while

Answer 1

that's too much code to go through line by line.  i'd recommend placing some trace() functions in strategic locations to narrow the location of the problem.