DNS Problem

i am having a problem with my dns server… i am having a network from 5 sites and one main site (HQR)i have a domain controller at each sit and two domain controllers at the (HQR) one as primary and one as secoundry…. and now i am trying to connect the users to the domain but it seems that it takes more than 15 minuts to connect to the domain after that i tried to ping the domain using its name the resolved IP address seams to be on of the remot sites not for the (HQR).. so what could be the problem…. please help me