To add to the issue: the problem only surfaces when I POST a form to the server, here are a few of examples from the /var/log/nginx/access.log file :
==================
127.0.0.1 - - [07/Jan/2013:17:29:14 +0800] "GET /admin/logout HTTP/1.1" 302 0 "https://iossapp1.com:9443/admin/iosIndex" "Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.11 (KHTML, like Gecko) Chrome/23.0.1271.97 Safari/537.11"
===============================
127.0.0.1 - - [07/Jan/2013:17:32:45 +0800] "POST /admin/editStaff HTTP/1.1" 302 0 "https://iossapp1.com:9443/admin/editStaff?staff.id=612" "Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.11 (KHTML, like Gecko) Chrome/23.0.1271.97 Safari/537.11"
127.0.0.1 - - [07/Jan/2013:17:32:45 +0800] "GET /admin/staffIndex HTTP/1.1" 304 0 "-" "Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.11 (KHTML, like Gecko) Chrome/23.0.1271.97 Safari/537.11"
==================================
127.0.0.1 - - [07/Jan/2013:17:35:45 +0800] "POST /admin/authenticate HTTP/1.1" 302 0 "https://iossapp1.com:9443/admin/login" "Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.11 (KHTML, like Gecko) Chrome/23.0.1271.97 Safari/537.11"
127.0.0.1 - - [07/Jan/2013:17:35:45 +0800] "GET /admin/masterIndex HTTP/1.1" 304 0 "-" "Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.11 (KHTML, like Gecko) Chrome/23.0.1271.97 Safari/537.11"


In contrast a GET URL behaves correctly like so :
127.0.0.1 - - [07/Jan/2013:17:36:21 +0800] "GET /admin/masterIndex HTTP/1.1" 200 2324 "-" "Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.11 (KHTML, like Gecko) Chrome/23.0.1271.97 Safari/537.11"

I noticed the numerical value after the response code (302, 304) that is 0 when the redirect is going to be unsuccessful, in the cases where it works, the numerical value is non-zero. What does this number represent?