I have now developed the miniBB solution for WordPress 2.5 and higher.
Download here.
I hope WordPress will not change their authorization anymore... it was a pain to investigate it. If not sponsored by
SlashGear staff, it would be impossible to work on it at all!
If you have WP-Cache plugin installed, it may happen that WP-Plugin caches forum pages; that way you don't see the new reply or topic coming right away. I recommend to disable WP-Cache for forum pages.
How to do that? It seems it's possible to exclude parts of the URL Request under WP-Cache settings (in WP admin, go to Settings -> WP-Cache and locate "Rejected URLs" section). There you will need to specify 'wp-forums' or any kind of folder where your forums are in. I hope it will work, because I wasn't able to test it on my side: this WP-Cache add-on is not working on localhost.