In normal case this indicates that the code want to have more access permissions then the ASP.NET are able to give to the application.

Solution for Windows 2008

In IIS manager select the site, in the features view double click .NET Trust Levels and select a higher trust level for your application.

Extremely strange behavior on a host running on VMware

This error seams to occur when a corrupt assembly exists in the application.

Solution

Replace all assemblies in the bin/ folder.

Version author:
Mattias Lövström

EPiServer version

'EPiServer CMS 5'