I ran into something a couple days ago. I'm programming in PHP and my authentication/session framework would not work on my local machine where I have apache virtuals tied to names I set up in Netinfo Manager like http://dev/

The cookie was successfully created and everything but was set for 'dev.local' which was not what I was browsing and so my session didn't work. Other browsers set the cookie for just 'dev' and I think this discrepancy is what, at least for me, is breaking my session handling. The same auth setup works fine on a remote server.