Дополнение
в логах содержится масса ошибок
cat /var/log/nginx/error.log


2011/01/04 22:02:40 [crit] 7705#0: *20382 chmod() "/var/tmp/nginx/proxy_temp/2/04/0061035042" failed (2: No such file or directory) while reading upstream, client: 95.188.204.215, server: , request: "GET / HTTP/1.1", upstream: "http://192.168.5.254:80/", host: "domen1.ru", referrer: "d1"
2011/01/04 22:02:40 [crit] 7705#0: *20382 unlink() "/var/tmp/nginx/proxy_temp/2/04/0061035042" failed (2: No such file or directory) while reading upstream, client: 95.188.204.215, server: , request: "GET / HTTP/1.1", upstream: "http://192.168.5.254:80/", host: "domen1.ru", referrer: "d1"

и тд... весь лог забит вот такими сообщениями