createLabel() method doesn't work

[dar]

My SBButton class extend extends UIComponent where I have declared an instance variable:
var lblText:TextField;

Further, in the createChildren() method I create this TextField instance:
lblText = createLabel("lblText", getNextHighestDepth(), "Button");
then I set the TextField instance as visible:
lblText._visible = true;
But the text doesn't appear (the trace() command shows wel 'Button'!)