Wanting to use open-uri and Net::HTTP under windows with proxy supporting NTLM/Kerberos authentication only

Our IT department decided to install Windows ISA server to proxy all of our
internet traffic. This server requires that any client authenticate via
Kerberos or NTLM. That works fine for IE or Firefox but it broke all my ruby
scripts that fetch various things from the internet for me.

Is anyone aware of code that allows open-uri or Net::HTTP to authenticate
with a proxy server that only supports NTLM/Kerberos? I don't necessarily
need an NTLM implementation in ruby - just a way forward to get the right
headeres into the web requests at the right time. Heck, if any Windows gurus
know the correct API calls to make to get the tokens out that I need that
will work too.

I have googled (and yahooed, and even 'ask'-ed) but to no avail. I found a
proxy server written in python (http://ntlmaps.sourceforge.net/) which will
work if I ask ruby to proxy through it, but otherwise I haven't found any
workable solutions.

Thanks in advance for any help!

Justin

p.s. I'm not real up on the terminology but NTLM seems distinct from
Kerberos - please forgive any mistakes above because of my misunderstanding.