Problems refreshing own Silva Product after Silva 1.5.3 Update - Not a registered directory: MyProduct/views

Dear Silva Developers,

I have written an own Silva product "ExtDocument" which is derived from 
SilvaDocument. After I updated my Silva from 1.4.2 to Silva 1.5.3 I get 
an exception if I try to refresh this product.

Traceback:
------------------------------------------------------------------------
Time  	2006/06/06 12:55:53.633 GMT+2
User Name (User Id) 	admin (admin)
Request URL 	http://localhost:8099/silva/service_extensions/refresh_all
Exception Type 	ValueError
Exception Value 	Not a registered directory: ExtDocument/views

Traceback (innermost last):

     * Module ZPublisher.Publish, line 114, in publish
     * Module ZPublisher.mapply, line 88, in mapply
     * Module ZPublisher.Publish, line 40, in call_object
     * Module Products.Silva.ExtensionService, line 89, in refresh_all
     * Module Products.Silva.ExtensionService, line 79, in refresh
     * Module Products.Silva.ExtensionService, line 53, in install
     * Module Products.Silva.ExtensionRegistry, line 119, in install
     * Module Products.ExtDocument.install, line 18, in install
     * Module Products.Silva.install, line 75, in add_fss_directory_view
     * Module Products.FileSystemSite.DirectoryView, line 526, in 
manage_addDirectoryView
     * Module Products.FileSystemSite.DirectoryView, line 494, in 
createDirectoryView

ValueError: Not a registered directory: ExtDocument/views
------------------------------------------------------------------------

Below is a code snippet from \ExtDocument\install.py.
The exception is raised in line 18:
   add_fss_directory_view(root.service_views, 'ExtDocument', ...

#----------------------------------
# \ExtDocument\install.py [Snippet]
#----------------------------------

import os
from Globals import package_home
from Products.Silva.install import add_fss_directory_view
from Products.SilvaDocument import externalsource
from Products.ExtDocument import ExtDocument

_custom_widgets_name = 'service_custom_widgets_ExtDocument'
_widgets_dir = 'widgets'
_permissions = ['Author', 'Editor', 'ChiefEditor', 'Manager']

def install(root):
     """The view infrastructure for Silva.
     """
     # create the extension views from filesystem
     add_fss_directory_view(root.service_views, 'ExtDocument', __file__, 
'views')

     # register views
     registerViews(root.service_view_registry)

     # create the widget editor views from filesystem
     add_fss_directory_view(root, _custom_widgets_name, __file__, 
_widgets_dir)

----------------------------------------------------------------

If I remove line 18, it raises an exception for line
   add_fss_directory_view(root, _custom_widgets_name, __file__,
with the same error:
   "ValueError: Not a registered directory: ExtDocument/widgets"


Any idea, what's going wrong there?

I saw a posting on the list at May, 15th where a user had problems 
installing SilvaFlexible with the same error, but that was caused by a 
incomptible version of SilvaFlexible with Silva 1.5.


Regards,
   Nico