did you follow the steps in the first document kdisc98 pointed to?
trying to build NPS policies (you need both a good Connection Request Policy and Network Policy) from scratch is tricky, better to go through the wizzard. once the basic works you can continue strip things you dont want, but the wizzard should give you something that works.
once it still fails it is indeed time to head for the windows event viewer and look for NPS events in the security section, these should be able to point you to the problem.