Vista - Microsoft.ServiceModel.Samples !!!!

Hey All

I am using Microsoft samples to see how things work in wcf. I tried
using the UserNamePasswordValidator project. it works fine when i am
using the generated proxy but when i try to use the service refence it
gives me following error:

call failed:
The X.509 certificate CN=localhost chain building failed. The
certificate that was used has a trust chain that cannot be verified.
Replace the certificate or change the certificateValidationMode. A
certificate chain processed, but hte terminated in a root certificate
which is not trusted by the trust provider.

i tried using various solution on net but unable to implement any!!!

please help me out.

thanks
sunny