Here is my setup:

JMS: 1.2.16
patches 1.2.22
Joomla 1.5.15

1 DB (each site with different prefix)

Dreamhost Shared platform

master site
1 slave site (for now)

components shared from master:

Community Builder
VirtueMart
JEvents
Kunena

Everything is sharing correctly from the master, except the users table, I've recreated the slave multiple times ensuring the template says share all virtuemart users and share Community builder but _users remains isolated.

This all worked great on localhost on MAMPPRO on a mac. I move into prodiuction and I have managed to get everything working except the _users. I cant log into the slave admin because the users don't exist.

ideas on what Im missing?

Im suspecting that my database doesnt allow those special kind of links or shortcuts to a physical table.

I remember I had some errors when importing my test DB into production on dreamhost.

Effectivelly, I suspect that when you have restored your DB that some tables (Views) was not recreated.

I suggest that you start to restore your master DB with JMS and that you resave your slave site to try creating the slave site tables and views.

The key element is that you restore correctly all the views.
I remember you need to have MySQL 5.0 and that the MySQL user must have enough privileges to create the views

I didnt realize you could use JMS to restore the DB, I was using phpMyAdmin

As soon as you have the master DB and the slave sites are built based on DB that does not contain links (views) then when you save the slave site, this "refresh" all the tables and views missing.
That mean that you start rebuild the slave site to have the correct links between the website and after restore your data with PHPMyAdmin

The idea is to start build the DB structure and in second step fill the DB with the data.
Only the master should be operational and also all the slaves that does not contains any "shared" DB tables.