User can not access their admin pannels after registration

Dear,
I am using S2 member integrated in http://viebuzz.com.
I have just configurated S2 member and everything go smootly, except my user can not access their admin pannel after checking out.
Please kindly advise me.
Thanks,
I am using S2 member integrated in http://viebuzz.com.
I have just configurated S2 member and everything go smootly, except my user can not access their admin pannel after checking out.
Please kindly advise me.
Thanks,