Exchange Server Setup Configurations

OS : W2K Server (As a Domain Controller)
Exchange Server : 2K Exchange Enterprise Server
Problem: Unable to logon Exchange Administrator Applicaions.
Error Message : The Microsoft Exchange Server Computer doesn’t respond.
Microsoft Exchange Directory
ID.No: DS_E_Communications_Problem.

Note:
a) I can able to strat and stop all exchange Server Serivces.
b) I can able to logon System Manager and control all the services.
3) I can able to create a mailbox andsend the mail service
4) My Interanet Mail Service will be working good.