Object doesn't support this property or method

The following works as expected:

var lbl = new SDI.ECS.Label();
lbl.setText("Hello");
document.write(lbl);

But this causes an error

var div = new Active.HTML.DIV;
var lbl = new SDI.ECS.Label();
lbl.setText("Hello");
div.setContent( "lbl", lbl );
document.write( div );

n html.js during evaluation of
this["{#0}"]();
I recieved the error in the title.



The superclass code that extends Active.System.HTML is

SDI.ECS.Component = Active.System.HTML.subclass();

/**
 * Base Object for the ECS Component Heirarchy
 */
SDI.ECS.Component.create = function(){

    var obj = this.prototype;
    var _super = this.superclass.prototype;

    obj.setClass("sdi", "component");

    obj.join = function(){
        var i, s = arguments[0];
        for (i=1; i<arguments.length; i++){s += arguments[i].substr(0,1).toUpperCase() + arguments[i].substr(1)}
        return s;
    };

    obj.refs = SDI.ECS.Component.refs = [];

    obj.defineProperty = function( name, defaultVal ) {
        var property = "__"+name;
        var getter = this.join( "get", name );
        var setter = this.join( "set", name );
        this[property] = defaultVal;
        this[getter] = function() {
            return typeof(this[property])=="function" ?
                   this[property].call(this) :
                   this[property];
        }
        this[setter] = function( val ) { this[property] = val; }
    }


    obj.defineProperty( "name", function(){return  "ECSComponent_"+this.getId();} );
    obj.defineProperty( "refId", function(){return this.getId();} );
    obj.defineProperty( "document", null );
    obj.defineProperty( "referenceNode", null );
    obj.defineProperty( "xpath", null );

    obj.defineProperty( "tooltip", null );
    obj.setAttribute("title", function(){ return this.getTooltip(); });

    obj.defineProperty( "debug", false );

    obj.debug = function( msg ) {
        if (this.getDebug()) {
            alert( msg );
        }
    }

};

SDI.ECS.Component.create();

And the Label code in my problem is

SDI.ECS.Label = SDI.ECS.Component.subclass();

/**
 *
 */
SDI.ECS.Label.create = function(){

    var obj = this.prototype;
    obj.setTag("span");
    obj.setClass("ecs", "Label");

    obj.defineProperty( "text", "Label" );

    obj.setContent( "labelText", function(){
        return this.getText();
    } );

};

SDI.ECS.Label.create();

In the debugger, the line

obj.setContent( "labelText", function(){
        return this.getText();
    } );

Gets a complaint that this.getText is not a property or method.
Any Idea why???

The following worked, but I still have no Idea why!

var div = new Active.HTML.DIV;
var lbl = new SDI.ECS.Label();
lbl.setText("Hello");
div.setContent( "lbl", function( ) { return lbl;} );

document.write( div );