i have the same problem. I'm using:
<fb:login-button rows="1" show-faces="true" width="960px" data-scope="email,publish_actions,user_birthday,user_about_me,user_relationships,user_location,user_website,user_education_history,user_activities,user_likes,user_interests,user_work_history,user_status,publish_stream" onlogin="javascript:jfbc.login.provider('facebook');" size="xlarge" v="2">Quick,Easy Registration using Facebook (Click Here)</fb:login-button>
All i get is "Quick, Easy Registration using Facebook"
the login button is not rendered. this work before i upgraded to 6.0. I do appreciate my subscription has just expired, but i have been with you guy for a long period. So hopefully that carries some weight.
Many thanks in advance