Since a while I have installed nginx and everything seemed to be working fine, recently I found out that about 20% of the time users are getting 502-errors. This is also noticable when Google tries to crawl my site in Webmaster Tools (from 10000 posts, approx. 2000 502 errors)

At first I was thinking to disable nginx, but I'd really like to keep using it. I'm running it on a server with 2GB RAM and 4 Reserved CPU Cores. WHM/cPanel installed and Mod_Ruid2 enabled + DSO as a PHP Handler with APC caching installed.

Is there anything I can change in the config, that can fix this?

I have installed Nginx Admin in WHM and here is what's in the configuration editor screen:

user  nobody;
worker_processes  4;
error_log  /var/log/nginx/error.log info;
worker_rlimit_nofile 20480;
events {
 worker_connections 10240; # increase for busier servers
 use epoll; # you should use epoll here for Linux kernels 2.6.x
}
http {
 server_name_in_redirect off;
 server_names_hash_max_size 10240;
 server_names_hash_bucket_size 1024;
 include    mime.types;
 default_type  application/octet-stream;
 server_tokens off;
 disable_symlinks if_not_owner;
 sendfile on;
 tcp_nopush on;
 tcp_nodelay on;
 keepalive_timeout  5;
 gzip on;
 gzip_vary on;
 gzip_disable "MSIE [1-6]\.";
 gzip_proxied any;
 gzip_http_version 1.1;
 gzip_min_length  1000;
 gzip_comp_level  6;
 gzip_buffers  16 8k;
text/plain text/xml text/css application/x-javascript application/xml image/png image/x-icon image/gif image/jpeg application/xml+rss text/javascript application/atom+xml;
 ignore_invalid_headers on;
 client_header_timeout  3m;
 client_body_timeout 3m;
 send_timeout     3m;
 reset_timedout_connection on;
 connection_pool_size  256;
 client_header_buffer_size 256k;
 large_client_header_buffers 4 256k;
 client_max_body_size 200M; 
 client_body_buffer_size 128k;
 request_pool_size  32k;
 output_buffers   4 32k;
 postpone_output  1460;
 proxy_temp_path  /tmp/nginx_proxy/;
 client_body_in_file_only on;
 log_format bytes_log "$msec $bytes_sent .";
 include "/etc/nginx/vhosts/*";
}

I hope someone can help me out.

Thanks in advance!