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Clearing a Layout in Qt

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I'm creating an application in Qt that allows users to drag around various "modules" in a QGraphicsView. Whenever one of these modules is selected, it emits a signal which is then picked up by a "ConfigurationWidget" which is a side-panel which should display all of the relevant parameters of the selected module:

class ConfigurationWidget : public QWidget

    ConfigurationWidget(QWidget *parent) : QWidget(parent) {}  

  public slots:
    void moduleSelected(Module* m)
        while (itsLayout->count()>0) 
          delete itsLayout->takeAt(0); 
      delete layout();

      itsLayout = new QFormLayout(this);
      itsLayout->addRow(QString(tr("Type:")),     new QLabel(m->name()));
      itsLayout->addRow(QString(tr("Instance:")), new QLabel(m->instanceID()));
      // ... Display a whole bunch of other fields that depends on the module

The problem is that the ConfigurationWidget never actually gets cleared when a module is selected. The new fields are just drawn over the old ones. I've tried various combinations of hide() and show(), invalidate(), update(), etc. to no avail.

What's the correct way to make a widget that can change its fields like this on the fly?

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