Our production BIZTALK 2006 R2 machine was restarted today but the Biztalk Host Instance services did not start automatically. There was an Event in the Systems Log that stated: The Enterprise Single Sign-On Service service hung on starting When I looked the SSO was started. From prior experiences this tells me that the service depends on another service but the registry did not contain that service. I'm assuming that SSO depends on MSDTC because the SSO db is on another machine. So I added MSDTC ......