Password Lockout of a user

I would highly recommend using Active Directory Audit by Lepide software. This software will tell you exactly what name and IP your account is being locked out on.

http://www.lepide.com/lepideauditor/active-directory.html

Will.

The eventlog on the DC already tells you where the lockout happened.
Visit that computer, see who was logged on while it happened. Now look for these 4:
scheduled tasks using that locked account
services using that account
scripts using that account
saved credentials using that account
You'll find it.

At the bottom of Event ID 4740 where the user account locked out is reported, the "Caller Computer Name" field is there.
The value contains the name of the computer from where the lockout is generated.
Do you mean that this computer is the DC ?
If you follow the instructions from McKnife then you should be able to find out why this happened.

@Will, the question states that the Account Lockout Tool was used.
I don't know exactly which tool was used and maybe you already know but Microsoft provide some free tools for this.
https://technet.microsoft.com/en-us/library/cc738772(v=ws.10).aspx
http://www.microsoft.com/download/en/details.aspx?displaylang=en&id=18465
https://www.microsoft.com/en-us/download/details.aspx?id=15201

The IP recorded in the event log is the IP of one of my DC's.

I will examine the logs tomorrow.

Thanks

It is locked out at some DC, always,  because it is a domain account. But the event log also tells you, where that bad password was being used.

To understand and find that: Stage a lockout with a test account and have it lockout on your own workstation. Then look into the logs at the DCs searching for your own IP.

Thanks for your response. The important field is not the IP-address but the name of the computer which is mentioned in the "Caller Computer Name". If you follow McKnife's instructions then you will be able to compare.

Here is the error

- <Event xmlns="http://schemas.microsoft.com/win/2004/08/events/event">
- <System>
  <Provider Name="Microsoft-Windows-Security-Auditing" Guid="{54849625-5478-4994-A5BA-3E3B0328C30D}" /> 
  <EventID>4771</EventID> 
  <Version>0</Version> 
  <Level>0</Level> 
  <Task>14339</Task> 
  <Opcode>0</Opcode> 
  <Keywords>0x8010000000000000</Keywords> 
  <TimeCreated SystemTime="2015-06-30T13:36:43.873284800Z" /> 
  <EventRecordID>866403047</EventRecordID> 
  <Correlation /> 
  <Execution ProcessID="508" ThreadID="2240" /> 
  <Channel>Security</Channel> 
  <Computer>xxxDC01.xxxlaw.local</Computer> 
  <Security /> 
  </System>
- <EventData>
  <Data Name="TargetUserName">ahmeda</Data> 
  <Data Name="TargetSid">S-1-5-21-663965598-47014434-1039276024-1338</Data> 
  <Data Name="ServiceName">krbtgt/xxxLAW.LOCAL</Data> 
  <Data Name="TicketOptions">0x40810010</Data> 
  <Data Name="Status">0x18</Data> 
  <Data Name="PreAuthType">2</Data> 
  <Data Name="IpAddress">::ffff:192.168.94.207</Data> 
  <Data Name="IpPort">55633</Data> 
  <Data Name="CertIssuerName" /> 
  <Data Name="CertSerialNumber" /> 
  <Data Name="CertThumbprint" /> 
  </EventData>
  </Event>

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Thank you for pointing that event id out.  
I saw in the initial call by the user that the computer in question was the possible root of the issue and I asked him to logoff or reboot the machine. He said he did, but he never did.
I then rebooted the machine and all was good after that.

Thanks for you help all.

Thanks for the information and very good to hear that it's solved.