LINQ not updating on .SubmitChanges()

DataClasses1DataContext db = new DataClasses1DataContext();
 User updateUser = db.Users.Single(e => e.user == user);
 updateUser.InUse = !updateUser.InUse;
 db.Log = new System.IO.StreamWriter(@"c:templinq.log") { AutoFlush = true };
 db.SubmitChanges();