Incrorect User Name and Password Error

My Scenario

1. 4 x VMs (1 x Windows Server 2008R2 Domain Controller, 1 x Windows Server 2008R2 client & 2 x Windows Server 2003 clients)

2. 3 x client machine are domain joined.

3. server 2003 machines are accessible via rdp and no issue.

4. When 2008R2 machine accessed from 2008R2 management machine, gives user name / password error continuously, when same machine accessed from 2003 client, logon is successful.

5. Local admin logon to machine is sucsessful and all domain related tasks are performed with no issue, accept domain user credentials at every prompt.

6. DNS working fine. ping to domain controller and vice versa fine.

what is the reason of incorrect user name and password while i am entering correct one.

Thanks for reply