CRM 2013 Online - fail login to pluginregistration

Hi,

I cannot succeed to make a connection using PlugInRegistration tool for my instance of Microsoft Dynamics CRM Online (Trial Version). I downloaded recently the SDK and using PlugInRegistration tool version 6.0.0000.0809. On my CRM Online instance, I accessed the Developer Resources and copied from there the URL to the Discovery Service. It looks like this:

https://disco.crm4.dynamics.com/XRMServices/2011/Discovery.svc

I tried to make a connection using PlugInRegistration tool, with this URL and the user used to login to my CRM online instance and it fails. I found also this article where it says that the URL should be written using "crm5" and not "crm4":

http://dynamicday.wordpress.com/2013/11/05/crm-2013-plugin-registration-tool-connect-to-crm-online/

Anyways, I tried also with "crm5" instead of "crm4" and it still does not work. The error I receive is:

Unhandled Exception: System.IO.FileNotFoundException: Could not load file or assembly 'Microsoft.IdentityModel, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35' or one of its dependencies. The system cannot find the file specified.
   at Microsoft.Xrm.Sdk.Client.ServiceMetadataUtility.RetrieveLiveIdIssuerEndpoints(IdentityProviderTrustConfiguration identityProviderTrustConfiguration)
   at Microsoft.Xrm.Sdk.Client.ServiceConfiguration`1.AddLiveIssuerEndpointsToCrossRealmIssuers(IdentityProviderTrustConfiguration identityProviderTrustConfiguration)
   at Microsoft.Xrm.Sdk.Client.ServiceConfiguration`1.SetAuthenticationConfiguration()
   at Microsoft.Xrm.Sdk.Client.ServiceConfiguration`1..ctor(Uri serviceUri, Boolean checkForSecondary)
   at Microsoft.Xrm.Sdk.Client.ServiceConfigurationFactory.CreateConfiguration[TService](Uri serviceUri)
   at Microsoft.Xrm.Sdk.Client.ServiceProxy`1..ctor(Uri uri, Uri homeRealmUri, ClientCredentials clientCredentials, ClientCredentials deviceCredentials)
   at Microsoft.Crm.Tools.PluginRegistration.CrmConnection.get_DiscoveryService()
   at Microsoft.Crm.Tools.PluginRegistration.CrmConnection.RetrieveOrganizations()
   at Microsoft.Crm.Tools.PluginRegistration.ConnectionsForm.OpenConnection(CrmConnection con)

Can u please help?

Thank's a lot,

Lorena