Setup NT trust relationship

We have a tunnel set up between main office and CA office. Both server can ping each other. I tried to setup 2-way trust between two domains but no luck. First, I got error “can not locate domain controller” and then according to Microsoft notes,I changed some registry setting on both server. Now I got error “password is incorrect” when I tried to set up the trusted domain. I tried both domain’s administrator password. Please help!