App runs OK but DB not updating... no error given or exception thrown.

Creating new desktop C# DB driven project or using Visual Studio 2005 sample project, Movie Collection... both have the problem.     Am using SQL Server 2005 Express.  Am using Windows Autentication.  Programs run and everything looks OK;  but, the database does not get updated.   There are no error messages or failures noted.  The database is simply not changed (CRUD).

This looks like a windows write priviledges problem as no program or DB error is given.   The data just goes down the bit bucket.  There is probably something in a log somewhere but I don't know where to look.   What is the default application user ID when an application connects to the DB.  Need to change an XML file somewhere?  What?  Any ideas?

thanx, marc