OK, one issue down, no longer receiving 403 errors. However, after the post, the script is supposed to redirect to the member landing page (another cgi program), and all we are getting is the registration login page returned with the user name filled in (blank password). Looking through an HTTP sniffer, I can see the post to Register.cgi working fine, but no 302 header is ever created. I can move (and have) the Register.cgi to my Unix box, and it works correctly.

update: found a cryptic reference that you must set at least one Mime type in IIS for redirect to work. Testing on in-house server and it appears to be making a difference. Will update again after checking client server.