The configSource file 'App_Data\EntityClasses.config' is also used in a parent, this is not allowed.
Reason: both a Web site and a virtual folder under that web site have the same physical path, e.g. 'c:\Inetpub\wwwroot\EasyProjects'.
Solution: Either remove a virtual folder under the web site - if you want EP to be run as a separate web site,
change a physical path of the web site to 'c:\windows\temp' (for example) - if you want to run EP under a virtual directory.