Problem Using X509 certificate for security

Hi,

I tried working on WCF. I am able to find out many things in WCF.

I am trying to implement X509 Certificate concept with my code.

While downloading through samples from the link:
http://www.microsoft.com/downloads/details.aspx?FamilyID=2611A6FF-FD2D-4F5B-A672-C002F1C09CCD&displaylang=en,

I am trying to use this Example: "WCF_WF_CardSpace_Samples\WCF\Extensibility\Security\X509CertificateValidator\CS"

I am getting some error. The error description is:

"The certificate 'CN=' must have a private key. The process must have access rights for the private key"

I have given all the access rights to the certificate using the command:

cacls.exe
"C:\Documents and Settings\All Users\Application
Data\Microsoft\Crypto\RSA\Machinekeys\4d657b73466481beba7b0e1b5781db81_c225 ...