PB.NET: error -401 (user unauthorised) when calling REST WS with basic auth

I was going through Y.Werde's article on calling RESTful WS from PB.NET 12.6:

http://www.codeproject.com/Articles/271588/RESTful-Web-Services-A-Quick-Start-How-to-Guide

but it seems that listing 3 always returns error -401 (user unauthorised) when accessing the service with BASIC authentication.

I've also tried a different REST service (e.g. https://api.github.com/user) but same error. 

Is it a bug in the PB.NET WCF infrastructure?

Best,

Marco