FYI,
As far as my problem is concerned to be unable to upgrade to 0.9.1, I have removed the “old” directory (not any php files higher in the structure) and installed 0.9.1 as “first time”.
This went okay. I had to change wp-config.php and .htaccess (manually as instructed) and then it went okay.
Be aware that automatically upgrade did however not work.
Thanks again,