WebSetup: Unable to build folder named <foldername>

[wvanhoye]

I created a WebSetup project for a standard ASP.NET
application. This ASP.NET application has 2 folders:
ParentFolder1 and ParentFolder2. Both these folders have
two subfolders ChildFolderA and ChildFolderB. Each
subfolder contains one webform.

Like:
ParentFolder1
----ChildFolderA
--------WebForm1A.aspx
----ChildFolderB
--------WebForm1B.aspx
ParentFolder2
----ChildFolderA
--------WebForm2A.aspx
----ChildFolderB
--------WebForm2B.aspx

The ASP.NET application builds succesfully.

When I compile the WebSetup project I get following error:
ERROR: Unable to build folder named 'ChildFolderB'

When I remove one of the WebForms and build again
everything goes well.

Remark: This phenomena occurs also with other resource
items. Such as text-files, htm-files, ...