TFS 2012 RC - There is no agent with the name 'XXX' registered on the controller

If you see this error in the event log on the test agent:
Unable to connect to the controller on 'yyy:6901'. There is no agent with the name 'XXX' registered on the controller.

You will also be able to see the detailed error if you click on View Log while configuring the Test Agent:
V, 2012/08/08, 18:55:31.882, Observed that agent XXX does not exist. Microsoft.VisualStudio.TestTools.Exceptions.EqtException: There is no agent with
the name 'XXX' registered on the controller.
Server stack trace:
   at Microsoft.VisualStudio.TestTools.Controller.AgentManager.GetAgentMachine(String agentName)
   at Microsoft.VisualStudio.TestTools.Controller.AgentManager.GetAgentProperties(String agentName)
   at System.Runtime.Remoting.Messaging.StackBuilderSink._PrivateProcessMessage(IntPtr md, Object[] args, Object server, Object[]& outArgs)
   at System.Runtime.Remoting.Messaging.StackBuilderSink.SyncProcessMessage(IMessage msg)
Exception rethrown at [0]:
   at System.Runtime.Remoting.Proxies.RealProxy.HandleReturnMessage(IMessage reqMsg, IMessage retMsg)
   at System.Runtime.Remoting.Proxies.RealProxy.PrivateInvoke(MessageData& msgData, Int32 type)
   at Microsoft.VisualStudio.TestTools.Execution.IControllerCommands.GetAgentProperties(String agentName)
   at Microsoft.VisualStudio.TestTools.ConfigCore.TestControllerHelper.AgentExists(String agentName, IControllerCommands controllerCmds)

The fix is to make sure that while configuring the test agent, you type the test controller name in the same case as the computer name of the test controller. So if the computer name of the test controller is YYY, make sure that you type YYY and not yyy