No WPMU site defined on this host.

Apologies if this is covered elsewhere, but I've searched for the phrase which is the title of my post and didn't come up with a specific answer. I'm getting the above error message when I switch from standard WPMU to the Multi-DB code. It should be noted that if I remove the db.php and db-config.php files, I go right back to a merrily-swinging WPMU installation.

I'm using the released 1.0.1 version of the Multi-DB files. The way I have it set up currently is to have my old db as the global db for now, with the root blog's tables in the VIP database. The add_vip_blog call reflects this. I'm using the 16-database setup. I'm using my host's shared IP address for the dc_ip and host IPs in the add_db_server calls. I've tried switching to 'localhost' for this information, but with the same results. All the usernames and passwords are identical.

Server information: Apache 2.2.9 (Unix), PHP 5.2.6, MySQL 5.0.45-community-log on a Linux server.

Thanks for whatever help you can send my way!