Problems upgrading to 6.11 with nginx

Hi all,

I have a multisite installation of Drupal 6.10. Trying to update to 6.11 I get a strange behaviour running update.php (in every site), i.e. the only db update needed is system 6050, but when I hit "upgrade" I'm taken to the home page of the site.

Nothing is written in drupal's logs.

These are the relevant rows of web server's logs:

www.domain.com - - [05/May/2009:09:47:40 +0000] "GET /update.php HTTP/1.1" 302 5 "-" "Mozilla/5.0 (Windows; U; Windows NT 5.1; it; rv:1.9.0.10) Gecko/2009042316 Firefox/3.0.10"
www.domain.com - - [05/May/2009:09:47:41 +0000] "GET /update.php?op=info HTTP/1.1" 200 1462 "-" "Mozilla/5.0 (Windows; U; Windows NT 5.1; it; rv:1.9.0.10) Gecko/2009042316 Firefox/3.0.10"
www.domain.com - - [05/May/2009:09:47:46 +0000] "POST /update.php?op=selection&token=67fd45208bb3a67412ae987a56124b3d HTTP/1.1" 200 2366 "http://www.domain.com/update.php?op=info" "Mozilla/5.0 (Windows; U; Windows NT 5.1; it; rv:1.9.0.10) Gecko/2009042316 Firefox/3.0.10"
www.domain.com - - [05/May/2009:09:47:57 +0000] "POST /?op=selection&token=67fd45208bb3a67412ae987a56124b3d HTTP/1.1" 200 8469 "http://www.domain.com/update.php?op=selection&token=67fd45208bb3a67412ae987a56124b3d" "Mozilla/5.0 (Windows; U; Windows NT 5.1; it; rv:1.9.0.10) Gecko/2009042316 Firefox/3.0.10"

and this is the nginx virtual server:

    server {
        listen       80;
        server_name  www.domain.com *.domain.com;  # Multiple hostnames seperated by spaces.  Replace these as well.

        charset utf8;

        access_log /home/nando/logs/access.log main;
        error_log /home/nando/logs/error.log warn;

        if ($host = 'domain.com' ) {
            rewrite  ^/(.*)$  http://www.domain.com/$1  permanent;
        }

        location = / {
            root   /home/nando/web/drupal6;  # Again, replace this. 
            index  index.php;
        }

        location / {
            root   /home/nando/web/drupal6;
            index  index.php index.html;

            if (!-e $request_filename) {
                rewrite  ^/(.*)$  /index.php?q=$1  last;
              #  rewrite ^/(\w*)/(.*)$ /$1/index.php?q=$2 last;
                break;
            }
        }

        # serve static files directly
        location ~* .+\.(jpg|jpeg|gif|css|png|js|ico|pdf|zip|tar|gz|bz|bz2)$ {
             access_log off;    #/root/uffa.log main;
             root /home/nando/web/drupal6;
             expires 30d;
        }


        # imagecache needs to have php read any files that it's planning to manipulate                                                 
        location ^~ /fatt/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;
            }
        } 


        error_page  404              /index.php;

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

        location ~ .php$ {
          fastcgi_pass   127.0.0.1:9000;  # By all means use a different server for the fcgi processes if you need to
          fastcgi_index  index.php;
          fastcgi_param  SCRIPT_FILENAME  /home/nando/web/drupal6$fastcgi_script_name;   # !! <--- Another path reference for you.
          fastcgi_param  QUERY_STRING     $query_string;
          fastcgi_param  REQUEST_METHOD   $request_method;
          fastcgi_param  CONTENT_TYPE     $content_type;
          fastcgi_param  CONTENT_LENGTH   $content_length;
        }

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

	 include /etc/nginx/awstats;
     }

I've changed my domain name into domain.com

Does anyone have an idea of what is going wrong?

Thank you in advance