Здравствуйте, RendeRR, Вы писали:

RRR>Такая ошибка:
RRR>

RRR>The HTTP request is unauthorized with client authentication scheme 'Basic'. The authentication header received from the server was 'Basic realm="pc"'.

Где хостится служба? Под IIS?
Вот тут http://msdn.microsoft.com/en-us/library/aa702565.aspx есть спец пометка для этого случая:

When a WCF service is hosted in Internet Information Services (IIS) using transport-level security and the UserNamePasswordValidationMode property is set to Custom, the custom authentication scheme uses a subset of Windows authentication. That is because in this scenario, IIS performs Windows authentication prior to WCF invoking the custom authenticator.

Попробуй в эту сторону покопать.