Interesting, i'm unable to reproduce it with the uri. The uri generates a pdf file (when it does not exist on the fs). I've deleted it on the fs and it's created fine by our php application. I've also made some tests with keepalive off, no change.
Maybe there is something missing in SLES 10 which is required by 1.1? A manual configure and make (without install) with my nginx -V runs without errors.

My fastcgi_params:
set $php_root /docroot;
root $php_root;
try_files $uri $uri/ @404;
fastcgi_pass php-fpm_backend;
fastcgi_keep_conn on;
fastcgi_index index.php;
fastcgi_param SCRIPT_FILENAME $php_root$fastcgi_script_name;

fastcgi_param QUERY_STRING $query_string;
fastcgi_param REQUEST_METHOD $request_method;
fastcgi_param CONTENT_TYPE $content_type;
fastcgi_param CONTENT_LENGTH $content_length;

fastcgi_param SCRIPT_NAME $fastcgi_script_name;
fastcgi_param REQUEST_URI $request_uri;
fastcgi_param DOCUMENT_URI $document_uri;
fastcgi_param DOCUMENT_ROOT $document_root;
fastcgi_param SERVER_PROTOCOL $server_protocol;

fastcgi_param GATEWAY_INTERFACE CGI/1.1;

fastcgi_param REMOTE_ADDR $HTTP_X_FORWARDED_FOR;
fastcgi_param REMOTE_PORT $remote_port;
fastcgi_param SERVER_ADDR $server_addr;
fastcgi_param SERVER_PORT $server_port;
#fastcgi_param SERVER_NAME $server_name;
#fastcgi_param HOST_LSG $http_host;
fastcgi_param HTTP_REFERER $http_referer;
fastcgi_param HTTPS $https_ms;

fastcgi_pass_header HTTP_HOST;
fastcgi_pass_header SERVER_NAME;
fastcgi_pass_header HOST;
fastcgi_pass_header SERVER_NAME;
fastcgi_pass_header X-REAL-IP;
fastcgi_pass_header X-FORWARDED-PROTO;
fastcgi_pass_header X-FORWARDED-FOR;