Hi folks! I am having trouble throughout my network with users getting this error in their message composition windows from time to time. Downloading the address book fixes this but it returns sometimes. And again it is multiple people that see this behavior. Does anyone know what can cause this and can be done to fix it? It only started recently and we have been using this Exchange/Outlook configuration for a while now. We use Exchange 2010 fully updated with fully updated Outlook 2010.