PEAP and domain logon

Hi! I have followed this excellent tutorial: http://homepages.lu/charlesschwartz/radius/freeRadius_AD_tutorial.pdf and it works perfect!! I have checked the option "automatically use my windows logon name and password..." on my XP Clients, but only users who has been logged in before can log in again, because of their cached credentials. To me is the "chicken or the egg" dilemma, does anyone have a solution for this issue? Thanks, Christoffer