The problem is that the widget sometimes receives a disable-message before it is created.
Solution is
_setDisabledAttr : function(value) {
logger.debug(this.id + "._setDisabledAttr");
this.isInactive = !!value;
if (this.comboBox) // <------ add this line
this.comboBox.attr("disabled", this.isInactive);
},
All widgets should be investigated for the need of this change.