I don't fully grasp the relationship between 'slugs' and forum topics, and would appreciate a nod in the right direction.
I can see that when permalinks are set to None, the forum.php file is fed an ID and then grabs the topic(s). When I originally set up one of the forums I set the permalinks to Name based (pretty..?) and all worked fine. However, I moved the forum into a sub-folder, and changed the URI in the topicmeta DB table, so the forum index page appears in the browser. But, while I can navigate fine with permalinks set to None (ie., topics passed by number), it refuses to work when set to Name.
I realised this might be the slugs in the DB, and so tried removing one and switching permalinks off/on. It fails to find the topic page. If I set permalinks back to None, it works ok.
Am I right in assuming it's using the slugs for topic navigation? If so, is there a way of rebuilding the slugs so that they work within the new sub-folder? (And incidentally, why are they called 'slugs'..?)