Custom taxonomy page not displaying

I’ve created a custom taxonomy for a content type that I’ve made, and I can’t get the listing to work when I use permalinks.

The code that I’ve used to create the taxonomy is straight out of many examples that are seen around the place:
register_taxonomy ("productcategories", array ("ourproducts"), array ("hierarchical" => true, "label" => "Product Categories", "singular_label" => "Category", "rewrite" => true, "public" => true));

When I remove the permalinks and use the defualt “?=123” settings, I can see the pages as expected and the page lists the items that are set ofr that term, but when I use the “Post name” setting for permalinks (or any of the other settings) I get a 404 page.

I’ve trie deverything from changing the permalink settings, deletinng the .htaccess. file, changing the catgory slug so that I know that it’s unique, but nothing seems to help.

Is there something specail that I have missed, or is this just not going to work?