I am having the same issue as Michael. I have a server with NCM on a non-internet connected system, and I am unable to import the .xml files.
I am an Administrator on the machine as well. I feel many of the people that will be downloading these STIGs have systems deployed on servers that are either non-internet connecting or their Administrative credentials will prevent them from browsing the Internet. Can you load the generic NCM exports for the STIGs?
Thanks