I received the following exception today in my local azure development environment when debugging my application.
The error message goes on to say, "Cannot write configuration file" refering to my ApplicationHost.config, meaning that whatever is writing to that file either cannot open the file as its locked or does not have persmissions. I cannot verify either case as no inner exception existed so I'll need to check through the appfabric docs to discover what this is about.
The solution however was simple in my case and perhaps it can help you solve a similar issue.
What I did was cleaned out my VS project/solution and restarted both my Computer and Storage emulators.
This seem to fix whatever was broken.