Addendum:

The failure occurs when I attempt to create a folder coming from the Portfolio page.

But it succeeds when I use the Create New menu item (which I assumed meant only a story/document).

Perhaps it's me misunderstanding the functions of the pages... but then again, I happened to be on the Portfolio page and it did take me to the same Folder creation page. So, in a month or so, when I want to create another, I may end up doing it again and wondering why it failed... so I don't know.

Thanks again.