Entourage 2008 & Exchange 2010

My work mail servers were upgraded to Exchange 2010. My mail clients are on Entourage 2008 with the web services patch applied. I am having problems getting the root certificate to be recognized from Entourage while inside my corp. network.

Does anyone else have any experience connecting Entourage 2008 to Exchange 2010 ? I have until tomorrow afternoon to get this working and am getting desperate! thanks.