Unexpected element tag "SOAP-ENV:Envelope" seen

Hi,

we get this error message on every request we are trying to send via gSOAP:

Unexpected element tag "SOAP-ENV:Envelope" seen

Could anyone explain me, why i get this error?

Here is the request:

POST /sdk HTTP/1.1
Host: vmware-test.boreus.de
User-Agent: gSOAP/2.8
Content-Type: application/soap+xml; charset=utf-8; action="urn:vim25/5.0"
Content-Length: 551
Connection: close
Accept-Encoding: gzip, deflate
SOAPAction: "urn:vim25/5.0"

<?xml version="1.0" encoding="UTF-8"?>
<SOAP-ENV:Envelope

    xmlns:SOAP-ENV="http://www.w3.org/2003/05/soap-envelope" xmlns:SOAP-ENC="http://www.w3.org/2003/05/soap-encoding"

    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"

    xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:ns1="urn:vim25"><SOAP-ENV:Body>

<ns1:RetrieveServiceContent xsi:type="ns1:RetrieveServiceContentRequestType">

<ns1:_this xsi:type="ns1:ManagedObjectReference" type="ServiceInstance">ServiceInstance</ns1:_this>

</ns1:RetrieveServiceContent>

</SOAP-ENV:Body>

</SOAP-ENV:Envelope>

And here the answer:

HTTP/1.1 500 Internal Server Error
Date: Wed, 7 Sep 2011 16:51:10 GMT
Set-Cookie: vmware_soap_session="524dac01-d304-ac9d-c557-34839dde76ac"; Path=/; HttpOnly;
Cache-Control: no-cache
Connection: close
Content-Type: text/xml; charset=utf-8
Content-Length: 565

<?xml version="1.0" encoding="UTF-8"?>
<soapenv:Envelope xmlns:soapenc="http://schemas.xmlsoap.org/soap/encoding/"
xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/"
xmlns:xsd="http://www.w3.org/2001/XMLSchema"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
<soapenv:Body>
<soapenv:Fault>
  <faultcode>ClientFaultCode</faultcode>
  <faultstring>
Unexpected element tag &quot;SOAP-ENV:Envelope&quot; seen

while parsing HTTP request before method was determined
at line 1, column 0</faultstring>
</soapenv:Fault>
</soapenv:Body>
</soapenv:Envelope>