Visual Studio 2008 renames App.config files to the corresponding module file name appending the ".config" extension. The previous version looks for "App.config" only so this is not working with VS2008.
For fixing this issue, we need to change the default config file name as the full .Net System.Configuration, using the current module file name appending the ".config" extension.
Additionaly, we'll need to:

• Include a ConfigFileName property on ConfigurationManager to allow an arbitrary config filename like "App.Config" for backward compatibility and tests.
• The property can only be set if the configuration is not loaded yet.
• Modify the unit tests that are using an aribtrary "App.config" as far as when running a unit test, the module name is the host and we need to force "App.config" as the config file name.