problem with BitmapData

[scottPadgett]

Hi,

I've started writing this class that draws a stripe of random color across the stage within certain parameters. I'm calling an instance of this class and then calling it's newLine() method 25 times in a loop with greater x coords passed in each time, to draw these stripes across the stage.

Sometimes it completely works, no errors, but often it will stop after a seemingly random number of cycles through the loop and give me this error:

ArgumentError: Error #2015: Invalid BitmapData.
at flash.display::BitmapData()
at LineMaker/newLine()
at lineMaker_test_fla::MainTimeline/frame1()

Here's the class code:

package 
{
    
import flash.display.MovieClip;
import flash.display.Bitmap;
import flash.display.BitmapData;
import flash.display.DisplayObject;
import flash.geom.Rectangle;
    
public class LineMaker 
    {

    private var lineCount:Number = 0;
    private var target_mc:MovieClip;
    private var bgWidth:Number;
    private var BMPD:BitmapData;
    private var BMP:Bitmap;
    
    //constructor
    public function LineMaker(target:MovieClip, bgWidth:Number)
        {
        this.target_mc = target;
        this.bgWidth = bgWidth;
        }
    
    //create a bitmap line
    public function newLine(wMax:Number, h:Number, xInterval:Number, xPos:Number, yPos:Number)
        {
        var w:Number = Math.random() * wMax;
        var xPosition:Number = xPos + Math.random() * xInterval;
        var thisColor:Number = getRandomColor();
        this.BMPD = new BitmapData(w, h, false, thisColor);
        this.BMP = new Bitmap(this.BMPD);
        var BMPref:DisplayObject = this.target_mc.stage.addChildAt(this.BMP, 0);
        BMPref.x = xPos;
        }
    
    private function getRandomColor(): Number
        {
        var color:Number = Math.random() * 0xFFFFFF;
        return color;
        }
    
    }
} 

Can anyone explain why I might be getting this error? I thought it might have something to do with the way I'm getting my random color value, but the error doesn't seem to be at all correlated to the color value at the time of failure...

Many thanks!