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
setErrorMessage(currentPage.getErrorMessage());
    }
    /**
     * Changes the shell size to the given size, ensuring that
     * it is no larger than the display bounds.
     * 
     * @param width the shell width
     * @param height the shell height
     */
    private void setShellSize(int width, int height) {
        Rectangle size = getShell().getBounds();
        size.height = height;
        size.width = width;
        getShell().setBounds(getConstrainedShellBounds(size));
    }
    /**
     * Computes the correct dialog size for the current page and resizes 
     * its shell if nessessary. Also causes the container to refresh its
     * layout.
     * 
     * @param page the wizard page to use to resize the dialog
     * @since 2.0
     */
    protected void updateSize(IWizardPage page) {
        if (page == null || page.getControl() == null) {
			return;
		}
        updateSizeForPage(page);
        pageContainerLayout.layoutPage(page.getControl());
    }