Multidb problem with clean installation

With WP3.0 i decided to start from scratch with multidb but for some reason, it’s not working.

I followed the installation and everything seems be fine, move-blogs worked without a problem, copied tables to vip blog but when i wanted to verify that im using the multidb (renaming the old db) i got the “Can’t select database” message.

The only thing that i did different now is the name of the db, the old db is called wp and the new wp_0, wp_1, etc. could that be a problem ?

Last time that i installed it i dont remember modifying the wp-config file, do we have to do it now ?