We were having an issue with orphan SQL sessions caused by a web application running on NT4/IIS 4. Turned out that when the application was moved to NT 2000/IIS 5 the orphan session problem disappeared. Suspect it was a combination of the application's compiled VB version and IIS version, since absolutely no changes were made to the SQL Server. A good discussion of the topic is found in the book, ADO Examples and Best Practices, by Vaughn (Apress, 2000)