COMException: The server threw an exception. (Exception from HRESULT: 0x80010105 (RPC_E_SERVERFAULT))

I am working in SharePoint Server 2001 to extract its contents. My code was working fine. But it is now throwing exception COMException: The server threw an exception. (Exception from HRESULT: 0x80010105 (RPC_E_SERVERFAULT)) from the following code

var _xmlHttp = new XMLHTTP60Class();
var xmldoc = new DOMDocument60Class();
_xmlHttp.open("SEARCH", "http://sanz/merosite/",false, "sanz","sanz"); // throws exception

I have checked it in google but couldn't found any relevant solution. I am using Interop.MSXML2 and Interop.PKMCDO dlls in my project. Please ! suggest