Is there a WordPress-related fix when your site is publicly visible but you can't access wp-adm

The site -- http://www.isi-companies.com/installation -- is publicly accessible but when I try to go to ../wp-admin, I get a dialog that says "Unable to load the webpage because the server sent no data. Error code: ERR_EMPTY_RESPONSE." I'm waiting to hear back from GoDaddy Support but I'm pretty sure they're going to say either there's nothing wrong or there's nothing they could do even if there is something wrong. Suggestions?