My Scenario on Windows VISTA, MySQL 5.5:

In cmd line I am able to enter 'mysql -u root -p' to enter MySQL shell after entering the correct password.
'USE myDB' or SHOW DATABASES' or 'SHOW TABLES' etc works here

Entering in 'mysqladmin -u root -h 'localhost' version variables -p'
I get the following error message:
'mysqladmin: connect to server at ''localhost'' failed'
'error: 'Unknown MySQL...