Drupal update from 7.22 to 7.23 - Internal Server Error 500

Drupal usual uptade procedure:

Backup your current site.
Switch your site to the maintenance mode.
Download and unzip the new Drupal core.
Remove the old Drupal files except /sites on the web server
Upload new version without /sites
If needed apply changes to the settings.php in /sites/default and edit sites specific entries (e.g. uname, pass, db, host)

If after the uploading new files you run into 500 internal server error you need to read this:

Simply speaking I had to make a significant replacement in .htaccess file:

instead