Wireless Authentication with NPS Machine Groups Policy

Hi

Long story short we have NPS setup with RADIUS client AP's to process wireless connection requests on our 2008R2 domain. Our Connection request and Network policies at present only contain a NAS Port Type 802.11 condition, which works fine. I am trying to restrict wireless access to computers that are part of the domain but as soon as I add a Machine Group condition which includes the Domain Computers group non of the computers can connect. I have seperately tested adding a User Group condition and this works fine. Any ideas on what could be wrong?

Thanks