Desperately seeking help on mysql error

[ChrisF79]

Greetings,

I want to make the forum on my site simply sit in the main content area with the left and right columns surrounding it, much like the main page http://www.understandfinance.com/ . To accomplish this, I include the navbar and leftnav through the code:

ob_start();
require("../includes/navbar.php");
$navbar = ob_get_contents();
ob_end_clean();

ob_start();
include_once('../includes/leftnav.php');
$leftnav = ob_get_contents();
ob_end_clean();

So this all makes sense, the mysql query that sits in the leftnav is as follows:

<?php
$dbh=mysql_connect ("localhost", "username", "password") or die ('I cannot connect to the database because: ' . mysql_error());
mysql_select_db ("understa_main", $dbh);
$query = "SELECT headline, newsstory, date_format(newsdate, '%M %D, %Y') FROM sitenews ORDER BY newsdate DESC LIMIT 3";
$result = mysql_query($query, $dbh);
while($query_data = mysql_fetch_row($result)) {
echo '<p><span class="bold">'.$query_data[0].'</span><br />'.$query_data[2].'</p>';
echo '<p class="story">'.$query_data[1].'</p>';
}
mysql_close($dbh);
?>

Then when I call the $leftnav in my header, I get an error from vbulletin that says:

Database error in vBulletin 3.0.3:

Invalid SQL:
SELECT
user.username, (user.options & 512) AS invisible, user.usergroupid,
session.userid, session.inforum, session.lastactivity,
IF(displaygroupid=0, user.usergroupid, displaygroupid) AS displaygroupid
FROM understa_session AS session
LEFT JOIN understa_user AS user ON(user.userid = session.userid)
WHERE session.lastactivity > 1101255492
ORDER BY username ASC

mysql error: Table 'understa_main.understa_session' doesn't exist

mysql error number: 1146


Now, understa_main is my database for my site that includes the tutorials, articles, etc. understa_forum is the database for vbulletin. So it looks as though vbulletin gets "stuck" so to speak, trying to access it's sessions table in my main database instead of it's own. The good folks over at vbulletin.com told me that this is where the experts are so I'm hoping someone can help me.

Sorry for the long post but I wanted to give you the full story.

Thanks in advance for any help you could provide!