Question about Outlook Express

In the past week when I open my Windows Live Mail to view my e-mails, I get a Security Alert message quite often stating "Revocation information for the security certificate for this site is not available.  Do you want to proceed?  The options are Yes, No, View Certificate.  Clicking the "View Certificate" says it is intended to ensure the identify of a remote computer, Issued by:  GTE CyberTrust Global Root, and gives a Certification path, Valid from 8/27/12 to 8/27/13.  I'm not sure if I should install this certificate or it it's from a hacker or a virus.  Has anyone experienced this alert or have a suggestion if it's safe?