xp and vista clients cant authenticate to osx server after kerberos is enablet

Hi All. I really have a big problem! My xeon xserve running 10.9 will not authenticate windows clients after I setup kerberos. There was no problem before with kerberos stopped. On my windows clients, when i try to bind them to the domain - they say unknown user. I try to bind them with my directory administrator account. What have I missed out? Do I need to configure something in the kdc admin? Any help is aprisiated