I can confirm the answer 1 solves the main problem (I am a new SE user, so I can not promote it yet). Here are the details for search engines:
From /var/log/nginx/error.log
2014/04/30 08:07:48 [crit] 35135#0: *116437 open() "/var/lib/nginx/proxy/7/09/0000001097" failed (13: Permission denied) while reading upstream
- , , nginx ( nginx config www-data /etc/nginx/nginx.conf).
chown -R correct_user:root /var/lib/nginx/proxy. , rm -rf 'd /var/lib/nginx/proxy , nginx correct_user .
eric-francis ! .