.NET Trust Levels in IIS Manager is set to Full (internal) Fiddler shows: <b> Description: </b>The application attempted to perform an operation not allowed by the security policy. To grant this application the required permission please contact your system administrator or change the application's trust level in the configuration file. ... <b> Exception Details: </b>System.Security.SecurityException: Request for the permission of type 'System.Security.Permissions.FileIOPermission, mscorlib, Version=4.0.0.0, ... failed.
What you can try to do is to set the trust level in IIS Manager to something else (let's say to medium), and then set it back to full immediately again. That will write the proper configuration to web.config file.
