im having this problem and my forums are in the root directory
mine are adding the /forum in to it...
this is my lines
line 221
$ibforums->vars['base_url'] = $forumpath . "/" . "arcade.php?".$sess."&";
$ibforums->base_url = $forumpath . "/" . "arcade.php?".$sess."&";
--------------- Added [DATE]1243563139[/DATE] at [TIME]1243563139[/TIME] ---------------
heres my arcade
http://www.diabeteschat.org/arcade.php