I tried this and it works:
Open the product-navbar_forumjump_1.0.4.xml file with an editor.
At line 85
Change:
Code:
$url = 'forumdisplay.php'.$sess_url.'f='.$forumid;
To:
Code:
$url = '../forums/forumdisplay.php'.$sess_url.'f='.$forumid;
Note: change "/forums/" to whatever your forums directory is.
Import and overwrite the product.
Update: This was fixed in version 1.0.7