I may have found something.
In /forumroot/global.php find this
PHP Code:
$bbuserinfo['user_avatar']="<a href='profile.php?{$session['sessionurl']}&do=editavatar'>{$bbuserinfo['user_avatar']}</a>";
And right before the "profile.php" part add in "forums/" (Or whatever your forums DIR is named & Without quotations) and see if that works.
Edit: Sorry that probably wouldn't work, put in your full forum URL, including site before the profile, like: "http://www.yourskite.com/forums/"