Drawing code problem

I’ve set up a simple drawing page here:

http://www.carlsonmedia.tv/drawing.html

for some reason, drawing left to right on the stage works fine. But right to left won’t work.

here’s the code action script 2.0 out of Flash CS3 pro:

lineThickness = 0;
selectedColor = “0x993333”;
_root.onMouseDown = startDrawing;
_root.onMouseUp = stopDrawing;
function startDrawing() {
if (_xmouse<455) {
_root.lineStyle(lineThickness, selectedColor);
_root.moveTo(_root._xmouse, _root._ymouse);
_root.onMouseMove = drawLine;
}
}
function drawLine() {
_root.lineTo(this._xmouse, this._ymouse);
}
function stopDrawing() {
delete this.onMouseMove;
}
line0.onPress = function() {
lineThickness = 0;
};
line3.onPress = function() {
lineThickness = 3;
};
line6.onPress = function() {
lineThickness = 6;
};
colorRed.onPress = function() {
selectedColor = “0x993333”;
};
colorGreen.onPress = function() {
selectedColor = “0x000000”;
};

also, if anyone could clue me in on where I can set the alpha levels for the drawing (what the code is and where it goes)