Webservices invalid header guid exception

I have a GUID & token to be passed whenever a webmethod (webservic开发者_如何学运维e) is called, from client app that is consuming the webservice.

1. Client app throws an "Error:undefined" javascript error & it gives this as exception when viewed via firebug.

System.Web.Services.Protocols.SoapException:

Invalid GUID Header.

System.Web.Services.Protocols.SoapMessage.RunExtensions(SoapExtension[] extensions, Boolean thrownException) at

System.Web.Services.Protocols.SoapServerProtocol.CreateServerInstance() at

System.Web.Services.Protocols.WebServiceHandler.Invoke() at

System.Web.Services.Protocols.WebServiceHandler.CoreProcesSRequest()

Any idea?

Thanks.