Permalink saved correctly in admin, but page 404s in front-end

[iparr]

I'm using the code:

'rewrite' => array('permastruct' => 'portfolio/%portfolio-category%/%postname%/'
),

…and it saves appropriately int the 'Permalink' field in wp-admin.

Unfortunately, when I visit that page I get a the 404 page.

If I change the code to:

'rewrite' => array('permastruct' => 'portfolio/cake/%postname%/'
),

…then visit that address, then it works fine. It's just the dynamic permalink that it slips up on.

Your thoughts appreciated as this plugin seems perfect for my needs, otherwise.