This class implements IUnknown and inherits the default implementation of IPropertyPageImpl.
Your class, derived from IPropertyPage2Impl.
Class IPropertyPage2Impl simply returns E_NOTIMPL for IPropertyPage2::EditProperty. However, it inherits the default implementation of IPropertyPageImpl and implements IUnknown by sending information to the dump device in debug builds.
When you create a property page, your class is typically derived from IPropertyPageImpl. To provide the extra support of IPropertyPage2, modify your class definition and override the EditProperty method.