Problem Encrypting the web.config file

I am trying to encrypt my web.config file. When it completes i get the errors

"the configProtectionProvider attribute is not declated"

"The element "appSettings" has invalid child element 'EncryptedData' in namespace 'http://www.w3.org/2001/04/xmlenc#" 

This is what i have in my web.config
<?xml version="1.0" Go to the complete details ...