I was working with this config from 2 years without any problem

sudenly I face not found error message from niginx

and its come only when the link has "?", sample
http://firmware.gem-flash.com/index.php?a=browse&b=category&id=1

if open the normal link, its working
http://firmware.gem-flash.com/index.php
http://firmware.gem-flash.com/[any other php file].php

site config (changed user info)

server {
listen *:80;
server_name firmware.gem-flash.com;
#error_log /var/log/nginx/firmware.gem-flash.com.log error;
rewrite_log on;
root /home/user/public_html/;

location / {
index index.php index.html index.htm ;
}

location ~*
^.+\.(jpg|jpeg|gif|css|html|png|js|ico|bmp|zip|rar|txt|pdf|doc)$ {
root /home/user/public_html/;
# expires max;
access_log off;
}


location ~ ^/.+\.php {
fastcgi_pass 127.0.0.1:9000;
fastcgi_index index.php;
fastcgi_intercept_errors on;
include /etc/nginx/fastcgi_params;
fastcgi_param SCRIPT_FILENAME $document_root$fastcgi_script_name;
fastcgi_param PATH_INFO $fastcgi_script_name;


}


}