Issue with AccesProfileReadAll. Client error.

I am trying to execute a AccessProfileReadAll and I'm getting the error "Client".

My other web services are working fine, so I know our session pooling is working.

Code:

    [WebMethod]
    public AccessProfile.AccessProfileData[] AccessProfileOD()
    {
        AccessProfile.AccessProfileService _ws = new AccessProfile.AccessProfileService();

        AccessProfile.AccessProfileReadAll_Input input = new AccessProfile.AccessProfileReadAll_Input();
        AccessProfile.AccessProfileReadAll_Output output = new AccessProfile.AccessProfileReadAll_Output();

        string sessionId = LoginDefault();
        if (_useProxy) _ws.Proxy = new System.Net.WebProxy("proxyserveraddress", 8989);

        try
        {
            _ws.Url = GetWSURL(sessionId);
           
            output = _ws.AccessProfileReadAll(input);
        }
        catch (Exception ex)
        {
            LogIt("AccessProfile->ERROR->" + ex.Message.ToString());
        }
        finally
        {
            Logoff(ConfigurationManager.AppSettings["CRMLoginURL"], sessionId);
        }

        return output.ListOfAccessProfile;

    }