user rights

i have windows 2000 server is a member server and i configured it as citrix server and i gave authencation by domain users. i added all domain users in local user groups and all domain users were working in citrix previousely. suddenly all users not able to access the published application in citrix server. i checked and added all domain users in local admion group now it is working. but i want to set it as old setup because of security problem.please help me? where will be the problem is there ?
user right? or os? or citrix server?