Notification doesn't work with Liferay

Hello,

I develop on liferay 6.2 with Vaadin 7.4.5.
I would like to use the Vaadin Notification :

Notification n = new Notification(“User add”, Notification.Type.HUMANIZED_MESSAGE);
n.setPosition(Position.MIDDLE_CENTER);
n.setDelayMsec(2000);
Page.getCurrent().showNotification(n); or n.show(Page.getCurrent());

It’s work but the Notification doesn’t disappear and it’s impossible to leave it.

Have you got any ideas ? Someone has already use Notification with Liferay 6.2 ?

Thanks.
Kevin