A co-worker of mine recently decided to "update to 3.5.1" without thinking twice or backing anything up. For a while the site was accessible to the public but not for the admins- our dashboard lead to a "fatal error" message. Now, when I try to access the site either as an admin or as the public, the page is white. What do I do!? How do I fix things if I can't access anything as an admin?