Once again WordPress has reworked the category system:
WordPress 2.3 introduces our new taxonomy schema. Any plugin that queries against the old table will break horribly. Plugins that use the category API should be fine.
This means that this code in my left sidebar, which I modified from the original Tiga theme:
<?php
$link_cats = $wpdb->get_results("SELECT cat_id, cat_name FROM $wpdb->categories");
foreach ($link_cats as $link_cat) {
if (get_links($link_cat->cat_id, '', '', '', FALSE, 'id', FALSE, FALSE, -1, FALSE, FALSE)) { /* anything to show? */
?>
needs some work. Looks like this evening’s project is figuring out how to use category filters.