ActionScript 2.0 :: MX04 - X_mouse And Browser Windows

I have this code on a mc PHP Code:

onClipEvent (enterFrame) {
this._rotation = (_xmouse / -100);
this._x = (_xmouse / -150);
}

This moves and turns mc on mouse position. This works fine but when I publish in a browser window something odd happens. If I open a blank second window and click between the 2 windows the mc will turn and move out of the window . I traced the _ymouse and _xmouse positions and found it jumps into -numbers. Does anyone known how to stop this from happening. I was thinking about using drag empty mc so it has something to focus on at all times. But their must be a better way of doing this.