Ok I tried a re-install.
Are there any known issues for having the forum installed in the root directory? I'm getting 404 errors all over the place.
I also have the google/yahoo sitemap generator installed, are there any conflicts with that?
edit: I re-installed yet again and also regenerated the .htaccess file and now it's working like a charm. Not sure what I missed the first few times around, but it's working now.