Movie Clip Not Playing Animation

I want to make an RPG game which uses turn-based battles. The problem is that my animations aren't playing when a specific button is pressed.

When the user presses the button labeled "attack", it will set the variable (ryu_action = 1).

On the next frame my animation will detect the variable and set it's "Alpha" value accordingly. My code for the Movie Clip object is the following:

onClipEvent (enterFrame) {

    if (_root.action_ryu == 1) {

        this._Alpha = 100;

        this.gotoAndPlay(4)

        _root.Ryu._Alpha = 0;

    } else {

        _root.Ryu_Attack._Alpha = 0;

    }

}

What I wanted was for multiple layers with objects that play one single animation in them overlapping a certain area. They will all hide/unhide themselves according to what action the user makes.

The problem I have here is that when the user presses the "Attack" button, the movie clip will follow the "gotoAndPlay" command and got to the fourth frame within the Movie Clip but it will get stuck on the fourth frame, not moving at all.

There is a "stop()" command placed on frame 1 of the movie clip but it's in it's own keyframe and shouldn't affect the rest of the animation within the movie clip.

My mentor has alerady told me that the code should be correct but it's just not running right for some reason.

I am using Actionscrip 2.0 on Adobe Flash CS3 Professional with a Windows XP computer.