I am having the same problem as I had before, but I am doing what I did to correct the problem last time.
On the instal mentioned in the link above I started by putting the user name in the php config file as grace_wrdp1 as that is the user name in cpanel/mysql. Error messages when I tried to access my site indicated that the user name was the problem so I changed it in db-config.php to grace which is my cpanel login and it all worked perfectly.
This time I am trying to instal 16dbs on another domain and in the db-config.php I have put the user name as horsefr1 but when I go to http://www.horsefr.com/wp-admin I get an error message asking if horsefr1_wrdp1 has permission to access the database. I haven't put horsefr1_wrdp1 in the config file so I don't understand what is happening. (I have tried putting horse_wrdp1 in the config file but get the same message) Move-blogs php works and the blogs are in their new dbs, if I remove db.php I can create new blogs which go into the old db but if I then upload db.php I can move the new blog into the new dbs so its just the connection thing again, only the solution that worked last time doesn't seem to be working.
Any ideas again?