EntLib - The application attempted to perform an operation not allowed by the security policy.

When using Enterprise Library Blocks you may end up with this error.  I used to have a blog entry on all of the specifics but I've lost that entry when my DB crashed several years ago.  I am dating this blog entry for that time period and who knows, I may yet try to recover my old DB.

Try the following to see if the issue can be fixed:
c:\winnt\Microsoft.NET\Framework\v1.1.4322\InstallUtil Microsoft.ApplicationBlocks.ExceptionManagement.DLL

HTH