Establish Trust with Windows 2000 Domain

Hi All,
I have 2 windows-2000 advance server DC in my organization into seperate network, and i want
to establish trust relationship between both of this, when i am adding
Trusted domain name and clicks on Add button it gives me an error that
“The RPC Server is Unavailable” but in Services RPC Service is Started
in both the servers.
so how can i start this RPC Server now…. ????
– Trust relationship on the same network works great. My firewall is wide open for these two network that needs to have trust relationships.
Thanks in advance!
Allen