[@mercime]

=== Do I need to make any changes to my bb-config.php file to run multisite? ===

Just to be clear, you had a single WP install with BuddyPress and created internal bbPress forums i.e. via BuddyPress forums set up, before upgrading to WP 3.0.4 and then creating a network/going multisite? Try to re-run Forum Setup. Backup database and server files, then go to dashboard > BuddyPress menu > Forums Setup > Use an existing bbPress installation – and in next panel point to your bb-config.php then click on “Complete Installation”