SQL Server 2008 R2 Implicit transactions

A single user connection will open animplicit transaction. The transaction will remain open until the user ends their session, or the connection is manually terminated (KILL (SPID)). Within 5  the open transaction begins to block other connections, the blocking escalates, and within a few minutes the application and server are overwhelmed by time outs. As soon as the initiating connection is closed, all problems resolve.

All configurations are set to AUTO COMMIT,IMPLICIT_TRANSACTIONS = OFF. No application code or system procedure changes this to our knowledge.We have no idea how the connection is switching to implicit transaction mode.

thanks

Phil