[Owncloud] owncloud 6.0 mysql user oc_admin already exists

[Hermann J Beckers]

I'm trying to install OC 6.0 on my server. There was no prior OC 
installation. Using advanced installation, I enter admin name/password 
and my MySQL credentials. owncloud returns with the above error message: 
Mysql user 'oc_admin'@'localhost' already exists. remove this user of 
MySQL. Hitting "finish installation" generates a config.php with sqlite 
as data store.

I then removed the oc_admin user with phpMyAdmin from MySQL user table,
removed date/admin directory, config.php and restarted the installation.
The result is the same. It makes no difference if I create the owncloud 
database before or let the installation script take care of it.

Any hints?
Hermann-Josef Beckers