Nginx – ‘No Input file specified’ error – NginX / fcgi – when requesting non-existant .php file

I have NginX serving a drupal site using fcgi. Attempting to browse to a non existent php file (eg. www.example.com/this-file-doesn't-exist.php) results in a white screen with this error:

'No Input file specified'

I used this post to help me set it up NginX:
http://drupal.org/node/110224

This is my NginX config file:

server {
listen 1.2.3.4:80 default;
server_name www.example.com;

client_max_body_size 6M;

root /var/www/example.com/;
index index.php;

error_page 404 /index.php;
error_page 403 /403.html;

# set up a location to serve static images for static error pages
location ^~ /error_images/ {
  root   /var/www/static_pages/error_pages;
  access_log        off;
  expires           30d;
}

# use our own custom 403 page
location = /403.html {
  root   /var/www/static_pages/error_pages;
}

# redirect server error pages to the static page /50x.html
error_page 500 502 503 504  /50x.html;
location = /50x.html {
  root   /var/www/static_pages/error_pages;
}

location / {
  error_page 404 index.php;
  error_page 403 /403.html;

  # the main drupal app
  if (!-e $request_filename) {
    rewrite ^/(.*)$ /index.php?q=$1 last;
  }
}

# hide protected files
location ~* \.(engine|inc|info|install|module|profile|po|sh|.*sql|theme|tpl(\.php)?|xtmpl)$|^(code-style\.pl|Entries.*|Repository|Root|Tag|Template)$ {
  deny all;
}

# serve static files directly
location ~* ^.+\.(jpg|jpeg|gif|css|png|js|ico)$ {
    rewrite ^/favicon.ico$ /sites/example.com/themes/exampletheme/favicon.ico break;
    access_log        off;
    expires           30d;
}

# imagecache needs to have php read any files that it's planning to manipulate
location ^~ /sites/example.com/files/imagecache/ {
   index  index.php index.html;
   # assume a clean URL is requested, and rewrite to index.php                                                                
    if (!-e $request_filename) {
        rewrite  ^/(.*)$  /index.php?q=$1  last;
        break;
    }
}

# serve the app via fastcgi
location ~ \.php$ {
    # ensure that a 404 is returned if a non existant php file is requested
    # doesn't seem to work properly, so commenting out
    # fastcgi_intercept_errors  on;
    fastcgi_pass unix:/tmp/php-fastcgi.sock;
    fastcgi_index index.php;
    fastcgi_read_timeout 240;
    fastcgi_param SCRIPT_FILENAME $document_root$fastcgi_script_name;
    include /etc/nginx/fastcgi_params;
}

# deny access to .htaccess files, if Apache's document root
# concurs with nginx's one
#
location ~ /\.ht {
     deny  all;
}

}

This post http://forum.slicehost.com/comments.php?DiscussionID=1259 suggests that it may be a a permissions error. However, I start fcgi as the user:group nginx:nginx, which is the same user NginX runs as.

In general, the configuration works just fine, and the site works 100% as it should. It is only when requesting a .php file that doesn't exist that the problem occurs. Requesting a .html file that doesn't exist for example results in Drupal serving it's 404 error page – which is what I want to happen for non existent .php files too.

ps. if you want to view that that url, please remove the extra whitespace after http:// – I don't have enough rep to post more than one hyperlink!