The more complex the network, the more complex the problem that can occur is. Here is a quick run down on some of the steps required in troubleshooting the domain controller locater process.
The process used by Windows computers to find a domain controller to authenticate to is one that is not completely problem fee. In the case that you experience this, here are a couple of quick steps you can do to track down where the problem lies.

Verify that you have network connectivity, and IP address, and can ping the domain controller you are trying to authenticate to.
Use the command: nltest /dsgetdc:domainname to ensure that the domain controller can be found for the domain specified.
Ensure that the server can be found in DNS with the command: nslookup servername.rootdomain.com.
Ensure that the SRV records for the domain controller are registered in DNS correctly with the command: nslookup guid._msdcs.rootdomain.com.
Use the Microsoft network monitor utility or another packet analysis application to see the exact step the domain controller locater process is failing on.
When troubleshooting this type of problem, it is always a good idea to understand how the process works in the first place. You can get a really good overview of this process by checking out the Microsoft KB article here: http://support.microsoft.com/kb/247811.

Article written by MyComputerAid.com