Error: System.Security.Permissions.FileIOPermission

If you are trying to run your .NET application and you are getting the following error: System.Security.Permissions.FileIOPermission
then most likely the problem is that your application is running in medium trust.  You will need to update your web.config to run in full trust. Please see the following article:

Changing the default ASP.NET Trust Level

http://support.webecs.com/KB/a672/changing-the-default-aspnet-trust-level.aspx