Well, I'm so disappointed right now

I followed just what is instructed in the Limitations section (I used define('FORUM_ABSOLUTE_PATH', '/path/to/my/forum'); ). I used to to replace the getcwd calls as well as the require_once('./global.php');
The error I reported above is now gone.
But now I think I'm experiencing a similar problem again. The call to vbsetcookie() fails:
path/to/vbulletin/includes/functions.php in vbsetcookie() function
Code:
else if (empty($vbulletin->db->explain))
{ //show some sort of error message
global $templateassoc, $vbulletin;
if (empty($templateassoc))
{
// this is being called before templates have been cached, so just get the default one
$template = $vbulletin->db->query_first_slave(" //this is line 1795
......
Fatal error: Call to a member function on a non-object in /path/to/forum/includes/functions.php on line 1795
I am using WP 2.2 & VB 3.6.7
WP is the root of my domain & VB is in a subfolder (named forum) of my domain