Fatal Error when using login integration

[simsportsworld]

Hi experts-

I have login integration working with vbulletin 3.5 on my site, the login code is as follows:

chdir('forums/');
require_once('/home/simsport/public_html/forums/global.php');

$userid=$vbulletin->userinfo['userid'];
$username=$vbulletin->userinfo['username'];
chdir('../');

This all works fine and i am able to see if im logged in. But at the very end of my page after all the output is displayed i get this error:

Fatal error: Call to a member function on a non-object in /home/simsport/public_html/forums/includes/functions.php on line 4240

I have this exact same code on another site and i dont receive any errors(and yes i changed the directory structure in require_once).

Any one have any ideas?

Rob