Issues with WP Plugins & Themes on IIS7/2008

I run a couple of in house WordPress sites for development on an old MacG4 PPC running Ubuntu 10.04LTS and it works perfectly. However, after a few installs on a Windows 2003R2 and Windows2008 32-bit servers everything works perfectly except I can browse themes or plugins from my WP Admin console. I know this can be a security issues anyway, but it is quite convenient to get notifications of updates to plugins with bug fixes. Also I have a few customers that are interested in running QP on their Intranet or Extranet sites to facilitate employee & customer communications and feedback on customer service. They all have Windows Networks and are not interested in working with Linux (sad creatures these business people, like little Lemming jumping off the Mountain of Microsoft into the sea of blue screens.) I also have these machines behind and older 2003 Small Business Server which does a great job publishing them out to the internet, but may be the culprit in my plugin and theme issue. I suspect this as the Ubuntu box is only behind a NAT router and gets all plugin updates and can browse for new plugins and themes without any issues. Any folks with some Microsquishy experience with running WordPress behind the SBS ISA 2004 server out there PLEASE HELP. I’m going nuts trying to figure this out and have to move on to more pressing issues.

Thanks Heaps,

Earth to Major Tom