Buffalo TeraStation Access Problem

I have 1 Buffalo Tera Station And i have problem in Access Restriction means when i put Nas in my Domain(windows 2003 Server Enterprise Edition)and nas is import users and i m create two folder in nas device. When i m doing access restriction in that two folder the whole group access restriction is done but whn i m doing simply user access restriction that is not done and show me erroe message “u not have permission to view this folder” and some times its again and again ask username password. plz help me what can i do in this senario.