802.1x on XP SP3 failed with "Identity: NULL"

Hi Everybody!

Server: Windows 2008 sp2 with AD, DNS, DHCP, NPS roles installed.

Client: Windows XP SP3 + KB957931 + KB960655.

802.1x configured via Group Policy. Computer only auth, using PEAP (Smart card or other certificate). Certificates issued for all domain computers via local MSCertificate Services (Windows 2003 server).

Problem description

Sometimes Windows XP SP3 computer failed to complete 802.1x auth at boot. Event ID 15514 from Dot3Svc. Identity: NULL, Reason: 327685, ErrorCode -2147024846 (0x80070032 - ERROR_NOT_SUPPORTED), Text: The request is not supported.

Second auth session had always completed successfully.

I have noticed that ip address had changed after such a failed auth.

So, my question is: why does it happen and how to prevent this?