i just had this issue too. try entering the entire database name. if it has a bunch of underscores and characters, enter those too.
it didnt work for me until i entered ‘user_com_-_database’ which is what Media Temple defaulted my database name too.
the prefix should be in this format: ‘user_’
goodluck.
For Media Temple subscribers that are stuck on this phase, use the ‘create database’ function in the MySQL databases menu to create the database name.
it should automatically give you some funky ‘user_com_-_yourdatabase’ kind of name.
use that entire name as your database name and the prefix should be ‘user_com_-‘
…otherwise youll get the cant locate server error.
hope this helps some folks traped out there!