For those who - like me - have had trouble when trying to enable SNC between SAP and BizTalk, I have posted an article on this subject a few minutes ago. Just follow the link :
http://geekswithblogs.net/SERivas/archive/2009/11/18/enabling-snc-to-communicate-between-biztalk-and-sap.aspx
It is very straight forward... Actually the only difficulty was to be able to tell an SAP Admin what I needed 
. Hope this will help some people...
Cheers!