There are a couple of us at $work with this problem.
We work on Macs, but as we're web developers we want to test using VirtualBox or Parallels etc.
In order to work with the corporate proxy, we put
proxy.corporationname.com/proxy.pac into our browser settings. Note, not just a proxy server, but a proxy.pac file with an NTLM proxy.
What settings should we put into our virtual browsers or our virtualisation system to get internet access through from the virtual OS to the host OS to the proxy to the internet?
I'd really like to hear from someone who's actually made this work.