The Salesforce.com client certificate is expiring on January 7, 2012 and a new certificate will be rolled out to production instances today. If you are a Salesforce.com customer using SAML authentication or 2-way SSL with Delegated Authentication or Workflow Outbound Messaging callouts, you may be affected by this change. Please read the details about this important update here and take any necessary remedial action as soon as possible.