authentication and active directory

Hi,

I have problem with authenticate user in active directory in asp.net.
I'm using code from http://msdn2.microsoft.com/en-us/library/ms998345.aspx
but I also start application on domain user. On my home test
environment I can authenticate by other user login and password, but
on client environment I can't. I don't know AD much and I wonder if
user on which application works should have special permissions for
authenticate users. BTW. on client's environment I can get number of
users in domain CN.

Regards,
Stefan

.