NHibernate exception: Transaction not connected, or was disconnected

Question

In our develop environment all the ASP.NET application works just fine. However, when I deploy the site on the test machine, on some pages I get this exception:

Answer 1

Another problem could be the user security (a database level exception again). In my case the underlying DB problem was:

The server principal "AppUser" is not able to access the database "AppDB" under the current security context.