Reinstall WordPress without messing up my site

Try the following:

1. Ftp: Go to the WP-content-folder and rename the install.php file to oldinstall.php.
2. browser: http://www.mydomain.com/wp-admin and it will ask you to update you wordpress. Do the update. After that you should be good.

Just do a manual update. Above is not required. If the update failed using the browser based admin interface once, I have no reason to think it would not again.

http://codex.wordpress.org/Updating_WordPress#Manual_Update

In a nutshell:

Remove only these two folders:

/wp-admin/
/wp-includes/

then upload new ones from a fresh download of WP3.5.2. Clear browser cache. Login. Test site.

Note: If using any server cache plugins, they should be deactivated when doing updates, including temp. turning off any CDN. If you do not have access to the admin, then rename the whole plugins folder in wp-contents to old-plugins before running the site.