How to avoid "too big header" issue?

[stalkercn]

nginx: nginx version: nginx/1.0.1
nginx: built by gcc 4.2.1 20070719  [FreeBSD]
nginx: configure arguments: --prefix=/usr/local/etc/nginx
--with-cc-opt='-I /usr/local/include' --with-ld-opt='-L /usr/local/lib'
--conf-path=/usr/local/etc/nginx/nginx.conf
--sbin-path=/usr/local/sbin/nginx --pid-path=/var/run/nginx.pid
--error-log-path=/var/log/nginx.log --user=www --group=www --with-debug
--http-client-body-temp-path=/var/tmp/nginx/client_body_temp
--http-fastcgi-temp-path=/var/tmp/nginx/fastcgi_temp
--http-proxy-temp-path=/var/tmp/nginx/proxy_temp
--http-scgi-temp-path=/var/tmp/nginx/scgi_temp
--http-uwsgi-temp-path=/var/tmp/nginx/uwsgi_temp
--http-log-path=/var/log/nginx-access.log --with-http_gzip_static_module
--with-http_stub_status_module --with-pcre

I decrease the fastcgi buffer size and increase the amount of buffers:
            fastcgi_buffer_size          64k;
            fastcgi_buffers           64 64k;

but a 'too big header' error still apears:

 [debug] upstream split a header line in FastCGI records
 [error]  upstream sent too big header while reading response header
from upstream

btw,php is working with Zend-Optimizer,whether this condition can make
the headers bigger than its real size?

Posted at Nginx Forum: http://forum.nginx.org/read.php?2,192785,195960#msg-195960