Discovery Accelerator webservice

[Spock]

When i am consuming the webservice from .net code i get the following error. 
{"System.Web.Services.Protocols.SoapException: Web service is not enabled.\n   at KVS.Accelerator.WebService.Discovery.GetCases(Boolean includeClosed, Boolean includeDeleted, Int64 usnGreaterThan, Int64& highUsn)"}

code below:

Discovery.Discovery _d = new Discovery.Discovery();
        _d.Credentials = new NetworkCredential("myuser","mypwd","mydomain");


        long usn;
        Case[] _case;

        _case = _d.GetCases(true, true, 0, out usn);

appreciate the help.