Bug in 802.1x stack (Windows XP)


I am testing 802.1x authentication in our network. The client I use for testing is one Windows XP SP1 and one with SP2.
Both have problems to authenticate the user. When I sniff the packets send by the XP Client I can see that Windows is using a wrong domain name. The switch sends the wrong login credentials to the IAS Radius server which denies the access request because the domain controller for this, wrong, domain can not be found.
Our domain is 3SOFT, normal login works, but when I enable 802.1x the domain name used by Windows in the EAPoL packets is "MDOFT".
So does anybody if there a fix for this problem?