Administrator Account got locked out frequently

There are two domain controllers on the network. Both of them are running on Windows 2003 Server. I found a warning sign in the log where it was return something about NTDS replication. The description of the error is "Active Directory could not update the following object with changes received from the domain controller at the following network address because Active Directory was busy processing information." Can anyone help me here to fix the problem. I am unable to get appropriate output on the same.

The problem that you are facing is related to NTDS replication. I am giving you a link which is having ample of information on the problem that you are facing. You can simply look into that and find out what is the exact issue you are facing. There are number of things which are associated with NTDS replication. And all of them are mentioned below in the link below. This would be more helpful to you.

Troubleshooting Active Directory Replication Problems

I am listing you some of the most common reasons due to which this kind of issue appear. You can simply check which one is applicable to you. The first is related to cache credential. Second you have to check ou the stale logon credential that are actually cached by store user name and password in CP. You have to disconnect the terminal session which are using stale credential. Sometime failure of AD to replicate between DC can cause the issue.