I'm not sure if it's WP or MultiDB or both :slight_smile:
On several installs of WP 3.0.1 (multi-site) and MultiDB 3.0.1 we're getting
Warning: mysql_error(): 21 is not a valid MySQL-Link resource in .../wp-content/db.php on line 291 Warning: mysql_real_escape_string(): 21 is not a valid MySQL-Link resource in .../wp-includes/wp-db.php on line 785
This happens sporadically, but in most cases when we try to change something in Super Admin -> Options.
Also, some boxes in Super Admin -> Options (like disk space quota) show up empty, although values are present in global DB.