Also a note..your original post said the app.app error was on this page.
Source File: c:\inetpub\wwwroot\Secure\Fenix\Default.aspx Line: 1
And now you say its on this page with the fenix.fenix error
Source File: c:\inetpub\wwwroot\Secure\app\Default.aspx Line: 1
These are two different Default pages....one in a Fenix directory and the other in the app directory....go to the default page of the Fenix folder..and do the same.
And just for sanity..if you have mulitple default pages in multiple "Secure" folders...
Go into each of them and remove the inherits by.....