New Post: Manual Upgrade 3.2 -> 4.0

I have completed all the steps, Composite seems successfully updated (so the backoffice says), but when I browse the pages I get errors. I looked on the log and I get this message

Failed to execute function: Layout.SyncroSystemOneColumn
20140725 16:35:56.8968 2 21 Error FunctionWrapper  System.ArgumentException: Supplied XDocument must have a root named html belonging to the namespace 'http://www.w3.org/1999/xhtml'

I got the same testing razor functions from the backoffice interface

Layout.SyncroSystemOneColumn result:
Failed to get value for function 'Layout.SyncroSystemOneColumn'
Supplied XDocument must have a root named html belonging to the namespace 'http://www.w3.org/1999/xhtml'

But the HTML content that was supplied and is still supplied has the namespaced specified, I don't understand what I am supposed to change on the content of the function...

Thank you in advance for your help

Sebastiano