This is due to Microsoft has tighten the security when you post data using the ServerXmlHTTP in MS XML Service Pack 2.
The original code you are using as follow :
set objXMLHTTP = Server.CreateObject( "MSXML2.ServerXMLHTTP.4.0" )
You will need to change the ProgID from MSXML2.ServerXMLHTTP.4.0 to WinHTTP.WinHTTPRequest.5.1.
For example :
set objXMLHTTP = Server.CreateObject( "WinHTTP.WinHTTPRequest.5.1" )
Note that you will need to replace the ProgID whenever there is an occurrence of the MSXML2.ServerXMLHTTP.4.0 in your code.