Keyset does not exist at Microsoft.Web.Services.Security.X509.X509

[Keyset does not exist X509Certificate]

I get this error trying to read de sign from a X509 Certficate Token X509SecurityToken.get_SignatureKey().

When I use the C# clases from windows applications its works, but when I do it from a .aspx page it hangs for a while then fails.

I allready set fullcontrol permissions to ASPNET user in C:\Documents and Settings\All Users\Application Data\Microsoft\Crypto\RSA\MachineKeys folder.

Thanks,