Movieclip scroller problem

I am trying to scroll a movieclip “scrollable_mc”. The movieclip is masked properly, but the scrollbar will not drag in the ‘gutter’ and the content will not move, any ideas folks? heres the code, the fla is at http://www.goelegant.com/scroller.fla

// mask the scrollable text
scrollable_mc.setMask(_root.mask_mc);

// determine the bounding area for the scrollbar drag
gutterTop = gutter_mc._y - 2;
gutterBottom = gutter_mc._y + gutter_mc._height - scrollbar_mc._height - 2;
gutterLeft = gutter_mc._y;
gutterRight = gutter_mc._y + gutter_mc._width;

// don’t use the hand cursor when the mouse is over the scrollbar
scrollbar_mc.useHandCursor = false;

// on entering the frame, see if the scrollbar is ‘dragging’
onEnterFrame = function() {
if(dragging = true) {
ypos = ypos + SPEED;
if(ypos > gutterBottom || gutterTop) {
dragging = false;
}
scrollable_mc._y = ypos;
}
else {
// do nothing, not dragging
dragging = true;
}
}

// when the scrollbar is pressed, start dragging
_root.scrollbar_mc.onPress = function() {
_root.scrollbar_mc.StartDrag(false, gutterLeft, guttterTop, gutterRight, gutterBottom);
dragging = true;
scrollbar_mc.onMouseMove = function() {
updateAfterEvent();
}
}

// when we let go of the scrollbar, throw the bar a little bit, adding a cool effect
scrollbar_mc.onRelease = function() {
this.stopDrag();
}