I think I was looking at the wrong place in the Log. One more thing i found this morning is that the "POST" is returning with a "HTTP/1.1 302 Found" in the AIX machine, where as the same code and same URL returns "HTTP/1.1 200 OK" in the Windows machine. Not sure where its trying to re-direct to. If I use  $mech->requests_redirectable([]); to avoid being redirected, it returns with a 302 and also says "Cannot Login...". Is there I way I can fetch the URL where it re-directs to, using Mech? I was hoping that Mech should take care of that itself, but looks like it isn't. My Windows machine is set to detect proxy server settings automatically and I dont see any re-direct when I try to open the login page in the browser.