Bug 134266 [Wizard] Page description not set if page message already set
Since page messages such as errors and warnings used to be displayed in the same widget as the page description, code was put in place in WizardDialog#updateDescriptionMessage() to avoid setting the page description if there was already a message. As of 3.2 M6 there is a separate widget for displaying error and warning messages and so the page description should always be set.
bundles/org.eclipse.jface/src/org/eclipse/jface/wizard/WizardDialog.java
update();
    }
    /**	
     * Shows the starting page of the wizard.
     */
    private void showStartingPage() {
        currentPage = wizard.getStartingPage();
        if (currentPage == null) {
            
            return;
        }
        
        if (currentPage.getControl() == null) {
            currentPage.createControl(pageContainer);
            
            
            Assert.isNotNull(currentPage.getControl());
            
            
        }
        
        currentPage.setVisible(true);
        
        update();
    }
    /**
     * A long running operation triggered through the wizard
     * was stopped either by user input or by normal end.
     * Hides the progress monitor and restores the enable state