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
Object state = null;
        if (activeRunningOperations == 0) {
			state = aboutToStart(fork && cancelable);
		}
        activeRunningOperations++;
        try {
            if (!fork) {
				lockedUI = true;
			}
            ModalContext.run(runnable, fork, getProgressMonitor(), getShell()
                    .getDisplay());
            lockedUI = false;
        } finally {
            activeRunningOperations--;
            
            if (state != null) {
				stopped(state);
			}
        }
    }
    /**
     * Saves the enabled/disabled state of the given control in the
     * given map, which must be modifiable.
     *
     * @param w the control, or <code>null</code> if none
     * @param h the map (key type: <code>String</code>, element type:
     *   <code>Boolean</code>)
     * @param key the key