Can't select database table even though the code is right

I am trying to display a list of my vbulliten threads on a non-vbulliten portion 开发者_如何学Pythonof my site. However I can't select the vbulliten database:

<?php

$host   = "localhost";
$user   = "my username";
$pass   = "my password";
$dbname = "tableprefix_forum";

mysql_connect($host, $user, $pass) or die ("Could not connect to database server.");
mysql_select_db($dbname) or die ("Could not select database.");

?>

I am substituting some things here in this example but all my credentials are correct including my db server username, password and forum db name. So what is the problem? Is it due to some internal security feature in vbulliten, does this system not allow you to connect to it's db if the page trying to connect to it is a non-vbulliten page?

Vbulletin has NO control over the permissions given by the server. But you do need to make sure that the user/pass you are using has been granted permission to access the database you are requesting.