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
* @see org.eclipse.jface.dialog.IPageChangeProvider#removePageChangedListener()
    */
	public void removePageChangedListener(IPageChangedListener listener) {
		pageChangedListeners.remove(listener);		
	}
 
	/**
     * Notifies any selection changed listeners that the selected page
     * has changed.
     * Only listeners registered at the time this method is called are notified.
     *
     * @param event a selection changed event
     *
     * @see IPageChangedListener#pageChanged
     * 
     * @since 3.1
     */
    protected void firePageChanged(final PageChangedEvent event) {
        Object[] listeners = pageChangedListeners.getListeners();
        for (int i = 0; i < listeners.length; ++i) {
            final IPageChangedListener l = (IPageChangedListener) listeners[i];
            SafeRunnable.run(new SafeRunnable() {
                public void run() {
                    l.pageChanged(event);
                }
            });
        }
    }
}