The following link is interesting re: what I said about edits I've made to /etc/hosts.

OS X Lion doesn't check the /etc/hosts file first. It checks it second. This is probably a bug but might be a "feature", but it's hard to work out what the reasoning is.

http://www.justincarmony.com/blog/20...ns-resolution/

And also this which mentions that it's not necessary to edit /etc/hosts on OS X any longer. http://tomafro.net/2009/07/dscl-the-...d-hosts-on-osx

My point is that OS X is caching the DNS from when you where connected to another network and not fully refreshing new DNS servers during the network transition.

I have ended up scripting this for clients as this issue effects loads of mobile users without them knowing it.....they just restart machine/tinker turning WIFI on and off and then all works fine....well i KNOW it is mDNSResponder as i have dealt with this very issue 100s of time.

Certain parts of OS X (the BSD bits) still can resolve /etc/hosts it is DNS resolution/search order that changed.

Unfortunately the Apple way is not always the best/right way and we have to lump it !

I think I've found my solution. Many thanks!

OK, the following seems to explain the issue and is pretty much what I've been experiencing:

http://apple.stackexchange.com/a/39076

I think the only reasonable solution is to add the domains they mention to the hosts file, so the look-up times out very quickly and you can get on with accessing the sign-on page.

This is a serious bug/oversight on behalf of Apple.

Edit: The (slightly insecure) solution to public hotspot/wifi connection issues, where you can connect but get a time-out when trying to sign-on via a browser, is to add the following lines to the bottom of your /etc/hosts file:

127.0.0.1 crl.usertrust.com
127.0.0.1 ocsp.usertrust.com
127.0.0.1 crl.incommon.org
127.0.0.1 ocsp.incommon.org

Be careful not to edit /etc/hosts with something like TextEdit, which will add the wrong type of line endings. I use nano at the command-line. If using something like TextWrangler, be sure to set the line encoding as "Unix (LF)".

Couple this with the way these Hotspots work....

You connect to their "special" network it provides a special DNS server which redirects any page request to a sign in page. You fill in details and it redirects you to the Public facing side which has different Public DNS servers...however the Mac still is using the old DNS server to try and resolve due to mDNSResponder being an awkward piece of crap (bet you are all feeling my love for it!)

DNS is so fundamental and Windows and Linux are generally very good as they have stuck with tried and tested methods of DNS resolution....Apple decided to do it a different way and have IMHO gone off course. It is certainly one of the key issues i deal with on a day to day basis and wish Apple would just nail it !

Didn't the Ubuntu people bugger around with DNS too? I agree that a simple solution is best, but engineers love to mess around with stuff.