Is this Safari 2 or Safari 3? And have you filed a Radar yet?
One thing I do is I have my /etc/hosts configured to map my machine name to 127.0.0.1. So for example:
That way, the URLs I use locally (and when not connected to either the corporate network or the VPN) still work when I email them to colleagues.
This also conveniently gets around the localhost cookie issue.