Multi-DB causing strange warnings

Hi gang,

Yesterday, I upgraded my WPMU installation to WP3, and I've been going through and updating all my mu-plugins as well.

I activated the latest version of Multi-DB, and everything works except for a few strange errors when accessing these pages:

SuperAdmin >> Users (/wp-admin/ms-users.php)
Dashboard >> My Sites (/wp-admin/my-sites.php)

Here is the error. When I access these two pages, this error repeats 20 times or more:

Warning: mysql_real_escape_string(): 15 is not a valid MySQL-Link resource in
 /home/ACCOUNT_NAME/public_html/wp-includes/wp-db.php on line 785

So, I checked the /wp-includes/wp-db.php file, and found this subroutine on line 785:

function _real_escape( $string ) {
if ( $this->dbh && $this->real_escape )
  return mysql_real_escape_string( $string, $this->dbh );
else
  return addslashes( $string );
}

I've tried several things to troubleshoot these errors, and I'm out of ideas at this point.
1. Disabled all /mu-plugins/
2. Disabled all /plugins/
3. Re-installed Wordpress files
4. Re-installed Multi DB plugin
5. Checked db-config.php file
6. Upgraded databases

Any ideas? The only other clue I could find (which leads me to believe this is a Multi DB thing) is this error:

Warning: mysql_error(): 15 is not a valid MySQL-Link resource in
/home/ACCOUNT_NAME/public_html/wp-content/db.php on line 291

See attached images as well. Any ideas?