Problem with multi-DB while establishing a connection to the database.

Hello there,
I just tried to install multi-DB. I followed exactly as you say in the instructions but I couldn't run well this plugin. I have all things updated.

The plugin generates an error_log file that says:
PHP Warning: mysql_free_result(): supplied argument is not a valid MySQL result resource in /home1/instan74/public_html/wp-content/scripts/move-blogs.php on line 140.

Problems it appears in browser when I try access to my website:
1. An error occurred while establishing a connection to the database.
2. Unable to select database
"We were able to connect to the server database (which means your username and password are correct) but you can not select the database instan74_global".

2.1. Are you sure it exists? --> Yes.
2.2. Does the user instan74_scholar have permission to use instan74_global database? --> Yes.
2.3. In some systems the name of your database is prefixed with your username, so it would be like username_instan74_global. Could this be the problem? --> My username in my database is exactly instan74.

Please, could you help me with this issue?. Thank you very much in advance.

Rodrigo

P.S: I had to choose a plugin to send this email, as multi-db not appears I put Anti-Splog.