Recently ran into an issue setting up a ScrewTurn Wiki site in a production environment. The production environment uses a local account as the identity for the application pool. After deploying the site I then went to visit it for the first time and the ScrewTurn wiki site gave me this exception:
[SecurityException: Request for the permission of type 'System.Web.AspNetHostingPermission, System, Version=18.104.22.168, Culture=neutral, PublicKeyToken=b77a5c561934e089' failed.]
After some checks to make sure the local account had the proper permissions to all of the necessary files, I finally tracked it down to a configuration setting on the Application Pool. By default all of the application pools on this server were configured with the App Pool not to load the user profile. Changing this to true resolved the issue.