Here is part of code in WizardDescriptor ( method "public void
actionPerformed(ActionEvent ev)" ) :

       
                        Runnable performFinish = new Runnable () {
                            public void run () {
                                err.log (Level.FINE, "performFinish entry."); //
NOI18N
                                Object oldValue = getValue();
                                    
                                // do instantiate
                                try {
                                    callInstantiate();
                                    setValueWithoutPCH(OK_OPTION);
                                    resetWizard();
                                } catch (IOException ioe) 
                                    // notify to log
                                    err.log(Level.FINE, null, ioe);

                                    setValueWithoutPCH(NEXT_OPTION);
                                    updateStateWithFeedback();

                                    // notify user by the wizard's status line
                                    putProperty(PROP_ERROR_MESSAGE,
ioe.getLocalizedMessage());

                                    // if validation failed => cannot move to
next panel
                                    return;
                                } catch (RuntimeException x) {
                                    // notify to log
                                    err.log(Level.FINE, null, x);

                                    setValueWithoutPCH(NEXT_OPTION);
                                    updateStateWithFeedback();

                                    // notify user by the wizard's status line
                                    putProperty(PROP_ERROR_MESSAGE,
x.getLocalizedMessage());

                                    // if validation failed => cannot move to
next panel
                                    return;
                                }
                                firePropertyChange(PROP_VALUE, oldValue, OK_OPTION);
                                
                                SwingUtilities.invokeLater (new Runnable () {
                                    public void run () {
					System.out.println( "---------- inside run just before firing action-----" );
                                        // all is OK
                                        // close wizrad
                                        err.log (Level.FINE,
"WD.finishOption.fireActionPerformed()");
                                        finishOption.fireActionPerformed();
                                        err.log (Level.FINE, "Set value to
OK_OPTION.");
                                        setValue (OK_OPTION);
                                    }
                                });
                                err.log (Level.FINE, "performFinish exit."); //
NOI18N
                            }
                        };

You can see that all debug information here is put into log with level 
Level.FINE. This concerns also exceptions. 
It is very hard to understand where is the problem for developer of wizard 
iterator ( its own implementation ) without any signals pointed to this problem.
I think ALL exceptions should be shown via ErrorManager with exception level,
not just logged with Level.FINE. Because level Level.FINE is very low level and
one need to know about this level and set it specially.