RPC server is not available

Hi there. I’m currently having problems connecting my BDC w/ Exchange 5.5 to my PDC in another site using a T1 connection. Whenever I try to synchronize it in Server Manager the message RPC server is unavailable is displayed. My ultimate goal is to connect this BDC w/ another BDC w/c has the main Exchange server to synchronize and move the mailboxes to the other exchange server. I can ping all of the names of the servers and it can be seen already on the PDC’s WINS server but it is not displayed in Network Neighborhood. Any suggestion is greatly appreciated.