Tooltip help

[FONT=arial][SIZE=3]Got this layout with previous and a next buttons and I’m trying to attach tooltips to both but when I get back to the first page I receive this error.[/SIZE][/FONT]
[FONT=Arial][SIZE=3][/SIZE][/FONT]
[FONT=arial][SIZE=3]RangeError: Error #2006: The supplied index is out of bounds.
at flash.display::DisplayObjectContainer/removeChildAt()
at Project_fla::MainTimeline/removeToolTip()[/SIZE][/FONT]
[FONT=arial][SIZE=3]Can anyone help tell me what’s wrong without me having to recreate the whole layout. Thanks. Here is the code:[/SIZE][/FONT]

[FONT=Arial][SIZE=3]var box_pos = 10;
var x_pos = -20; var y_pos = 10; [/SIZE][/FONT]
[FONT=Arial][SIZE=3]var tooltip:MovieClip = new MovieClip();
this.addChild(tooltip);[/SIZE][/FONT]
[FONT=Arial][SIZE=3]var txt:TextField = new TextField();
txt.multiline = true;
txt.autoSize = TextFieldAutoSize.LEFT;[/SIZE][/FONT]
[FONT=Arial][SIZE=3]var tf:TextFormat = new TextFormat();
tf.size = 14;
txt.defaultTextFormat = tf[/SIZE][/FONT]
[FONT=Arial][SIZE=3]function showTip(ttip,color,c1,c2,c3,c4)
{
tooltip.x = mouseX-x_pos;
tooltip.y = mouseY-tooltip.height-y_pos;
txt.htmlText = ttip
var h:Number = txt.height+box_pos;
var w:Number = txt.width+box_pos;
drawShape(txt.x-5,txt.y-5,w,h,c1,c2,c3,c4,color)
}[/SIZE][/FONT]
[FONT=Arial][SIZE=3]function drawShape(x,y,w,h,c1,c2,c3,c4,color)
{
tooltip.visible = true;
var shape:Shape = new Shape();
var graphic:Graphics = shape.graphics;
graphic.beginFill(color,.4); [/SIZE][/FONT][FONT=Arial][SIZE=3] [/SIZE][/FONT]
[FONT=Arial][SIZE=3] graphic.lineStyle(0,0x95969A);
graphic.drawRoundRectComplex(x,y,w,h,c1,c2,c3,c4);
tooltip.addChild(shape);
tooltip.addChild(txt);
}[/SIZE][/FONT]
[FONT=Arial][SIZE=3]function moveToolTip(event:MouseEvent)
{
tooltip.x = mouseX-x_pos;
tooltip.y = mouseY-tooltip.height-y_pos;
event.updateAfterEvent();
}[/SIZE][/FONT]
[FONT=Arial][SIZE=3]function removeToolTip(event:MouseEvent) {
tooltip.removeChildAt(0);
tooltip.visible = false;
}[/SIZE][/FONT]
[FONT=Arial][SIZE=3]nextBtn.addEventListener(“mouseMove”,moveToolTip);
nextBtn.addEventListener(“mouseOut”,removeToolTip);
nextBtn.addEventListener(“mouseOver”,function(){
showTip("<font color=’#000000’>Next Page</font>",0x95969A,17,17,17,17) [/SIZE][/FONT]
[FONT=Arial][SIZE=3] } [/SIZE][/FONT]
[FONT=Arial][SIZE=3] ) [/SIZE][/FONT]
[FONT=Arial][SIZE=3]prevBtn.addEventListener(“mouseMove”,moveToolTip);
prevBtn.addEventListener(“mouseOut”,removeToolTip);
prevBtn.addEventListener(“mouseOver”,function(){
showTip("<font color=’#000000’>Previous Page</font>",0x95969A,17,17,17,17) [/SIZE][/FONT]
[FONT=Arial][SIZE=3] } [/SIZE][/FONT]
[FONT=Arial][SIZE=3] )[/SIZE][/FONT]
[FONT=Arial][SIZE=3][/SIZE][/FONT]