[fel64]

There’s an easier way to do this, just put in the right domain.

//cookies

define('COOKIE_DOMAIN', '.2diabolos.com');

Or

//cookies

define('COOKIE_DOMAIN', 'forum.2diabolos.com');

If you go with the first, in my opinion neater version, you also need to add this to bbPress’ config.php.

//try to sync cookies

$bb->cookiedomain = '.2diabolos.com';

$bb->cookiepath = '/';

Then clear your cookies, log out and in and see if it works across your site.