Why do I get "SOAP Response Version Mismatch"

Following is the flex code to import a csv data file via c# webservice.

private function Import():void{
    CursorManager.setBusyCursor();

    var op:Operation = Operation(_webservice.getOperation('ImportData'));
    op.addEventListener(FaultEvent.FAULT,operationFault);
    op.addEventListener(ResultEvent.RESULT,operationResult);

    var ba:ByteArray = new ByteArray();

    ba.writeUTFBytes(objectToXML开发者_如何学编程(datasource.source).toXMLString());

    op.arguments = new Array(filename, ba);
    op.send();
}

protected function operationFault(e:FaultEvent):void
{
    CursorManager.removeBusyCursor();
    Alert.show(e.fault + " (" + e.statusCode + ")");
}


protected function operationResult(e:ResultEvent):void
{
    datasource.removeAll();
    CursorManager.removeBusyCursor();
    Alert.show("Success");
}

and following is the c# webservice:

[WebMethod]
public XmlDocument ImportData(String filename, byte[] data)
{
    Boolean bReturn = false;

    /* .... code to import data .... */

    XmlDocument xmlDoc = new XmlDocument();

    xmlDoc.LoadXml("<response>" + (bReturn ? "true" : "false") + "</response>");

    conn.Close();

    return xmlDoc;
}

The application works fine on my development environment, whereas when I run it on the production server I get the following error message:

[RPC Fault faultString="SOAP Response Version Mismatch" faultCode="DecodingError" faultDetail="null"] (404)

Development Environment is: Win7, MSSQL Server 2005, MS Visual Studio 2010, .NET Framework version 4.0.30319

Live Server: Win2008 Server, MSSQL Server 2005, IIS7, .NET Framework version 4.0.30319

Can anyone think of a reason regarding why I get the error message above on the live server?

Thanks.

---

I figured the problem. The data file I was trying to import was of 7MB text file. I split it into 2 files and tried to import then it worked. So the problem was the size of the data being transferred to the server.