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
private void restoreUIState(Map state) {
        restoreEnableState(backButton, state, "back"); 
        restoreEnableState(nextButton, state, "next"); 
        restoreEnableState(finishButton, state, "finish"); 
        restoreEnableState(cancelButton, state, "cancel"); 
        restoreEnableState(helpButton, state, "help"); 
        Object pageValue = state.get("page"); 
        if (pageValue != null) {
			((ControlEnableState) pageValue).restore();
		}
    }
    /**
     * This implementation of IRunnableContext#run(boolean, boolean,
     * IRunnableWithProgress) blocks until the runnable has been run,
     * regardless of the value of <code>fork</code>.
     * It is recommended that <code>fork</code> is set to
     * true in most cases. If <code>fork</code> is set to <code>false</code>,
     * the runnable will run in the UI thread and it is the runnable's
     * responsibility to call <code>Display.readAndDispatch()</code>
     * to ensure UI responsiveness.
     * 
     * UI state is saved prior to executing the long-running operation and is 
     * restored after the long-running operation completes executing.  Any attempt  
     * to change the UI state of the wizard in the long-running operation will be 
     * nullified when original UI state is restored.
     * 
     */
    public void run(boolean fork, boolean cancelable,
            IRunnableWithProgress runnable) throws InvocationTargetException,
            InterruptedException {