localhost working 127.0.0.1 broken in Safari

I'm running an http server on a non-standard port on a Mac Powerbook G4 running OSX 10.5.8 and attempting to open a page in Safari 4.0.4. When I use the IP address 127.0.0.1 in the url Safari shows an error:

Safari can’t open the page “http://12.34.56.78/” because the server where this page is located isn’t responding

where the IP address is the external IP of the m开发者_JAVA百科achine, so somehow Safari translates 127.0.0.1 to my internet-facing IP. When I use the alias 'localhost' in the URL it works as expected and shows the page.

The /etc/hosts file is as follows:

127.0.0.1   localhost
255.255.255.255 broadcasthost
::1             localhost 

Any ideas what might be happening here?

This SuperUser question has answers that suggest disabling IPv6, among other things.