I upgraded both my test websites to 3.5. Upgrade went fine, besides the problems I had with the temp file, when I tried to upgrade the themes and plugins. After I fixed this by adding define('WP_TEMP_DIR', '/tmp');
to my wp-config.php, I started the website, by going to the Home page.
This went fine, but now any page that I select gives me a Error 403.
I removed all files except my child thme folder and wp_config and copied the 5.3 files again, but the error stil happens, except for the home page.
Runinng Server 2008
PHP 5.4 (see http://www.nl1106.eu/info.php)