If you mean the custom page then this is waht I did. I took the post (single.php) and modified it thus; at the very top add
Template Name: forum-page.php
This identifies it as a new template. After the lines
<?php get_header(); ?>
Add this code;
<div id="forum-page" class="fullwidth">
Scroll to the bottom and remove any reference to sidebars if your theme supports them and save as forum-page.php.
In your style.css add this code (best placed in the structure bellow coment-in code);
and save. Go to write page and give a title of Forum, switch to HTML mode and add <!--WPFORUM--> then scroll down and in the page template drop down menu select your new template which is forum-page.php and save. Done.
I have 2 blogs with the same themes and same configuration but for the version of wordpress. Am using 2.6 on one and this set up works fine but with 2.6.2 the forum returns the above mentioned problem. I am assuming its a compatibility issue btwn wpforum and wp2.6.2.