The machine periodically fail 802.1x authentication. Also during the day, a system will be working fine and then suddenly fail auithenticaion and appear to lose network connectivity. Disabling the network card and re-enabling the card fixes the issue. The logs on the radius server seem to show that the client is refusing communication with the radius. We are using PEAP and we have unmarked validate the certificate, but the client still appears to be trying to validate the radius certificate.

I think this kb should work for you No response to 802.1X authentication requests after authentication fails on a computer that is running Windows 7 or Windows Server 2008 R2 http://support.microsoft.com/kb/980295