Why would the second code cause a parse error into the first one?

include("vbs_counter.php");

ob_start();
require("/var/www/aboutus/textads/textad.php");
$textads = ob_get_contents();
ob_end_clean();

What is in each file?

the first one is the vbstats hack and the second one is a non vbulletin related file, completely independent, that I use to display ads.

The way that I had it setup, vbstats convinces the advertisers and sells the ads, and the second non vb related file displays the purchase. That is the best polite, unobstructive way to display an ad that I found.
As per attached.

starts with this. Maybe the header location is doing it?

if (eregi("textad.php",$PHP_SELF)) {
Header("Location: /");
die();
} else
{
main();
}

I fixed it by harcoding the full path to admin/config.php in global.php instead of ./admin/config.php

That is peculiar how another file is throwing off vbulletin and taking over.