I am developing a web app using MVC 3 that is using standard form authentication. It is hosted on a shared hosting. The problem is that sometimes the user authentication state is lost. I get no exception at all. Do you have any clue what can be the cause?

Does authentication has anything to do with session? I am not using Session object at all.
I was of the impression that Authentication using cookie can work in a load balanced environment. Am I wrong?

The session is lost before the 20 minutes timespan.