I do not want to cause any confusion here... but I thought I would try a different configuration with my [Database type]

I changed all sites from mysqli to mysql and I receive this error in both [Manage Sites] records.

Warning: mysql_select_db(): 214 is not a valid MySQL-Link resource in /homepages/dotcom/libraries/joomla/database/database/mysql.php on line 135

The error

Warning: mysqli_select_db() [function.mysqli-select-db]: Couldn't fetch mysqli in /homepages/dotcom/libraries/joomla/database/database/mysqli.php on line 156

Mean that Joomla 1.6.0 is not able to connect on the DB.
This is like the user and password that you provide to connection on the DB Server is not able to select the DB name you specified.

The Errro

Warning: mysqli::ping() [mysqli.ping]: Couldn't fetch mysqli in /homepages/dotcom/libraries/joomla/database/database/mysqli.php on line 139

Let suppose that the "ping" function in MySQLi is not available or perhaps disabled by your hosting provider.
Perhaps you coud investigate on the Joomla bug reports concerning Joomla 1.6.0

We have tried reproducing what you described without success.

See the tutorial video 3 where we have added the version for Joomla 1.6.
tutorial.jms2win.com/joomla/multisite-12...stall-on-joomla-160/

Your video does not show my multisite configuration so I do not see why this tutorial will pertain to me.

In the video you are creating a (subdomain as the master) and a jms2win.com/master/slave as the slave.

In the video you never show multiple domains, you are using the same domain (jms2win.com) each time to create subdomains with the same database.

jms2win.com/
jms2win.com/master/
jms2win.com/master/slave1/
jms2win.com/master/slave1/slave2/

My multisite configuration is:

masterdomain.com
slavedomain1.com
slavedomain2.com
slavedomain3.com

And I am using separate databases not the same database, ther is a huge difference compared to what you demonstrate.

This is exactly the same in the video.
What ever the domain or subdomain or subdirectories, you written that you create a fresh slave site with a new Joomla installation using MySQLi.
This is what you can see in the video.
Change the domain name value does not change the creation of the slave site and the deploy directory does not change also the configuration.

This just demonstrate the the MySQLi ping function and the other "select" error that you report with the Joomla 1.6 library does not appear with our hosting company using cPanel.

Create and addOn Domain or a subdomain in cPanel with a "document root" give exactly the same result.
The database connection parameter is the one that you provide in Joomla Installer and not in JMS Multisites.
This is what is demonstrated with the Video and that the DB connection is correctly save and used by the slave.

If you want that we investigate on your server, we have a billable support that you can order at
www.jms2win.com/en/joomla-multisite?page...35&category_id=1

Were you able to figure this out? I am receiving the exact same error using a separate DB. I did a var dump on the $this variable and from what I see this list is trying to connect to the main DB rather than the separate DB. I am going to do some more digging since it is OBVIOUSLY our issue and not theirs.