HI Ant,
To configure Active Directory for wireless access, you got to determine whether you want to manage authorization by user or by group to design your own authorization scheme. NPS will grant or deny the network access authorization based on two configuration: Network Policies and AD user account dial-in properities.
To better understand this, you can refer to
http://technet.microsoft.com/en-us/library/cc732787.aspx or consult the book <<Windows Server 2008 Networking and Network Access Protection(NAP)>> Chapter 10. Page 332 Deploying Protected Wireless Access.
The troubleshooting part within this chapter also helps.
I hope this would help, if not, please feel free to reply to the same thread and provide us more detailed information.
Thanks,
Chao