You have been very careful and done everything you could do and it has still gone wrong. mmmThe only thing I can think of is there is a settingon the Server that has interfered with the ability to make the neccessary connections. Have the right permissions been granted? Seems silly but never know... Another issue lies in the database. Assuming your config.php file is accurate, btw, can you be sure that all address changes have been made in the database? Even running the replace.php can miss something.
Go to Site Administration > Plugins > Blocks > Manage blocks
And check to see if the plugin has actually been enabled. Then go and have a look at the database and see fio there is simething there that has been missed...
Sorry I cannot be any more help than this, this is disappointing for you, I am sure.
For anyone else reading this thread, the problem Luciano describes (caused by using admin/replace.php) has been reported in the Moodle Tracker as MDL-25352 and will hopefully be fixed in the next weekly build, available later this week.