If you see the “Configuration System Failed to Initialize” exception at run time, it is typically caused by an invalid entry in your app.config or web.config file. In my case, I encountered this exception when I had an “<add key…>” element out of place. Oddly enough, the compiler didn’t warn me about this when I rebuilt my solution with the config file open (as it usually does with most other config file errors).
Microsoft .NET MVP 2002-2009
Chief Architect, MM .NET Application Framework