WordPress permalinks turn forum into 404 pages

[gaso99]

I have WordPress installed on /public_html/ root folder. vBulletin forum is installed to /public_html/vb/. Now, if I set WordPress permalinks like this http://www.domain.com/%postname%/ the forum on the /vb/ subfolder bocomes unusable. Every url on the forum shows me a WP 404 error page.

This is what my htaccess looks like when the permalinks are on:

# BEGIN WordPress
<IfModule mod_rewrite.c>
RewriteEngine On
RewriteBase /
RewriteRule ^index\.php$ – [L]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . /index.php [L]
</IfModule>

# END WordPress

How can I exclude a folder from this rule so that i can access the forum? Turning permalinks off is not really an option because of seo.