Query Performance Manager Data for CPU Usage Fails

I was trying to run the below SOAP request to get the Performance data, but for some reason I'm getting an error shown below. Any reason why this would happen?

I'm using ESXi 5.1

Request

POST /sdk HTTP/1.1

Host: 10.6.6.10

Content-Type: text/xml; charset=utf-8

Content-Length: 635

Cookie: vmware_soap_session="5249778b-c80a-18b4-9881-5f8f3f5b2cae"

SOAPAction: "urn:internalvim25/5.1"

<soapenv:Envelope xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/" xmlns:soapenc="http://schemas.xmlsoap.org/soap/encoding/" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">

  <soapenv:Body>

    <QueryPerf xmlns="urn:vim25">

   <_this type="PerformanceManager">PerfMgr</_this>

   <querySpec>

    <entity type="HostSystem">ha-host</entity>

    <maxSample>1</maxSample>

    <metricId>

   <counterId>1</counterId>

   <instance></instance>

    </metricId>

    <intervalId>20</intervalId>

   </querySpec>

  </QueryPerf>

  </soapenv:Body>

</soapenv:Envelope>

Response

<?xml version="1.0" encoding="UTF-8"?>\n<soapenv:Envelope xmlns:soapenc="http://schemas.xmlsoap.org/soap/encoding/"\n xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/"\n xmlns:xsd="http://www.w3.org/2001/XMLSchema"\n xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">\n<soapenv:Body>\n<soapenv:Fault><faultcode>ServerFaultCode</faultcode><faultstring>The object has already been deleted or has not been completely created</faultstring><detail><ManagedObjectNotFoundFault xmlns="urn:internalvim25" xsi:type="ManagedObjectNotFound"><obj type="PerformanceManager">PerfMgr</obj></ManagedObjectNotFoundFault></detail></soapenv:Fault>\n</soapenv:Body>\n</soapenv:Envelope>