The official word from Opera is that it's an Opera thing:
"A host having an IP address that is either in the intranet range, or in the public network range (that is, not localhost) cannot access or automatically initiate resources on localhost, this includes redirects. The action have to be manual. (additionally, if the localhost server refuse access, requests to a hostname that is not "localhost" will just result in a blank resource, as that method is used for adbusting) Similarly, a host on a public network cannot automatically access resources on servers in the intranet range. Both these are implemented for security reasons, as this type access and redirects can be used to attack servers that are not otherwise available to the public network, and which as a result may have reduced defences against attacks (after all, "they are behind the firewall")." http://my.opera.com/community/forums/findpost.pl?id=2968737 Sorry for polluting the Twitter API thread with what turns out to be a browser feature, but at least now we all know. This really threw me last night.
