Random not really being random!#KL!@:

1

Hey i have this code i understand somewhat,

you can view it at www.amikamiami.com

My problem is that the randomness of this only apply to a part of the movie!! And it doesnt use the whole movie. what is wrong or what else am i missing?
the size of the movie is 477 width 312 height.

MovieClip.prototype.moveMe = function(begin, end, speed) {
if (this._x<=end) {
this._x += speed;
} else {
this._x = begin;
this._y = Math.random()*(64.5-0.5)+5;
}
};

and the movieClip

onClipEvent (load) {

this._y = Math.random()*(64.5-0.5)-5; 
var begin1 = (0 - (this._width / 2)) 
var end1 = (Stage.width + (this._width / 2)) 
var speed1 = Math.round (((Math.random() * 4) + 1))

}
onClipEvent (enterFrame) {
this.moveMe (begin1, end1, speed1)
}