Problem with MySQL/phpMyAdmin/Plesk (MySQL on my Webpage works just fine)

[archimedes@]

Hi there, I have serious Problems with Plesk/MySQL and phpMyAdmin.
I installed Zend Optimizer and it broke Plesk, so I uninstalled it and messed arround with php (updating to php4.4.4, changing the c:\windows\php.ini and downdating to php4.3.11 because IIS6 didn't accept the ISAPIs...), but now the button for accessing phpMyAdmin in Plesk is greyed out

If I try to change the MySQL-Username&Password in Plesk I get an Error:

Aktualisierung der Datenbank-Parameter fehlgeschlagen: Try to establish connection failed: Failed to connect to database: Can't connect to MySQL server on 'localhost' (10061)

(Translated: Updating the Database-Parameters failed: [...]

If I open the direct link to phpMyAdmin (https://**myserver**:8443/domains/databases/phpMyAdmin/) I get this error:

Es wurde kein Host angegeben!
Fatal error: Call to undefined function: pma_dbi_get_dblist() in C:\SWSoft\Plesk\admin\htdocs\domains\databases\phpMyAdmin\libraries\common.lib.php on line 1374

(Translated: The Host was not defined![...])

If I connect to MySQL using the commandline tool it works just fine and the Userdata in the psa/misc table is correct.
The PHP-Applications on my Website can still connect with their own users/databases without any problems, too...

Maybe the original php.ini can fix this error (though I *believe* I had an backup, but it didn't work as well... though, the whole Zendstuff completly shuffled me oO)

Please Help me...
Thanks, Sebastian

I use Plesk 7.5.6 for Microsoft Windows on a Windows2003 vServer...