Errors when running Cron
If I click "Run cron" in the admin menu I'm redirected to another URL.


You have a node using the PHP filter, and calling drupal_goto(). That node is then indexed, the PHP code is executed, and you are then redirect. Don't do that ;)


  I can't run cron; see the video capture I created.


You need to specify a cron key when accessing cron.php directly. You can find a link with the key on your Status report page (admin/reports/status).