The plugin did not work on me actually, there was some error, regarding wp_parse_args. So, I did some hacks on the code, and added information of the post author. The plugin should be working on you, I dont know whats the problem with the blog. WordPress have released a list of plugin that have been tested, working on WordPress 2.2 and WordPress 2.3.
Wp-forum – http://www.fahlstad.se/wp-plugins/wp-forum/
Wp-forum latest post plugin – http://www.schloebe.de/wordpress/wp-forum-latest-posts-plugin/
WordPress 2.2 compatibility – http://codex.wordpress.org/Plugins/Plugin_Compatibility/2.2
WordPress 2.3 compatibility – http://codex.wordpress.org/Plugins/Plugin_Compatibility/2.3