group replication issue on domain controllers

Hi

I have 2003 DFL & FFL, running on AD 2008R2 DCs in my domain.

I have one root domain and one child domain.

Now I have One application (PRS), which is getting authenticated to AD from group base. Like i have 2 group and the members of that group can reset password and other things in PRS tool.

But the issue is when I am pointing this PRS tool to LDAP://Dc=test,DC=tested,DC=com (name change), it works sometime and doesn't work sometimes.

But when I point this tool on one Perticular DC, it works fine and when I point to another DC then it doesn't work fine

I want to know why its happening..

please help me on this ???