Reverse Proxy from nginx won't run. Sites are normal - nginx

Question

There's some problem with my nginx. At first, starting is OK, surfing through the proxy is fast enough. But after a while, 5 -> 10 visit later, the proxy become slower and slower. Until it stop working. Even if i try to stop the nginx using "-s stop", double check if there are any nginx.exe running, and restart nginx. It's still not working.
Nginx.exe is still running.
Port is still in used.
I am running on Windows Server 2003 Enterprise Sp2 IIS6
This is the error i read from the log.
2010/08/20 21:14:37 [debug] 1688#3548: posted events 00000000
2010/08/20 21:14:37 [debug] 1688#3548: worker cycle
2010/08/20 21:14:37 [debug] 1688#3548: accept mutex lock failed: 0
2010/08/20 21:14:37 [debug] 1688#3548: select timer: 500
2010/08/20 21:14:37 [debug] 1580#5516: select ready 0
2010/08/20 21:14:37 [debug] 1580#5516: timer delta: 500
2010/08/20 21:14:37 [debug] 1580#5516: posted events 00000000
2010/08/20 21:14:37 [debug] 1580#5516: worker cycle
2010/08/20 21:14:37 [debug] 1580#5516: accept mutex locked
2010/08/20 21:14:37 [debug] 1580#5516: select event: fd:176 wr:0
2010/08/20 21:14:37 [debug] 1580#5516: select timer: 500
2010/08/20 21:14:38 [debug] 1688#3548: select ready 0
2010/08/20 21:14:38 [debug] 1688#3548: timer delta: 500
2010/08/20 21:14:38 [debug] 1688#3548: posted events 00000000
2010/08/20 21:14:38 [debug] 1688#3548: worker cycle
2010/08/20 21:14:38 [debug] 1688#3548: accept mutex lock failed: 0
2010/08/20 21:14:38 [debug] 1688#3548: select timer: 500
And this is the config file i wrote:
#user deploy;
worker_processes 2;
error_log /app/nginx/logs/error.log debug;
events {
worker_connections 64;
}
http {
include mime.types;
default_type application/octet-stream;
sendfile on;
#tcp_nopush on;
keepalive_timeout 65;
tcp_nodelay on;
gzip on;
gzip_min_length 1100;
gzip_buffers 4 8k;
gzip_types text/plain;
upstream mongrel {
server 127.0.0.1:5000;
server 127.0.0.1:5001;
server 127.0.0.1:5002;
#server 127.0.0.1:5003;
#server 127.0.0.1:5004;
#server 127.0.0.1:5005;
#server 127.0.0.1:5006;
}
server {
listen 81;
server_name site.com;
root C:/app/sub/public;
index index.html index.htm;
try_files $uri/index.html $uri.html $uri #mongrel;
location #mongrel {
proxy_set_header X-Real-IP $remote_addr;
proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
proxy_set_header Host $http_host;
proxy_redirect off;
proxy_pass http://mongrel;
}
error_page 500 502 503 504 /50x.html;
location = /50x.html {
root html;
}
}
}