FATAL ERROR on live site

I need ASAP Help!! Please.

Version: 3.0 WDP ID: 119 with db.php

The following is the error that appears on the browser when visiting the site.

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Warning: mysql_error(): supplied argument is not a valid MySQL-Link resource in /xxx/xxx/public_html/wp-content/db.php on line 291

Database Tables Missing.
Database tables are missing. This means that MySQL is either not running, WPMU was not installed properly, or someone deleted xxx_site. You really should look at your database now.
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xxx_site does exist with the proper content.

This was a working live site using define ('DB_SCALING', '16'); in the config file.

Now the script can't find the tables? weird.
I found this in my error log

[27-Jun-2010 14:35:20] WordPress database error for query SELECT p.post_title, p.post_excerpt, u.display_name FROM xxx_1_posts AS p LEFT JOIN (xxx_users AS u) ON p.post_author = u.ID WHERE p.ID='153' made by check_default_vars
[27-Jun-2010 14:35:20] WordPress database error: []
SELECT p.post_title, p.post_excerpt, u.display_name FROM xxx_1_posts AS p LEFT JOIN (xxx_users AS u) ON p.post_author = u.ID WHERE p.ID='153'