There has been a security breach identified with many Comodo Certificates. 

Comodo CEO Melih Abdulhayoglu calls the breach the certificate authority’s version of the September 11th terror attacks!

If you’re running Windows you need to apply this patch immediately.

http://support.microsoft.com/?kbid=2524375

If you’re using Mac or Linux, this affects you too, however I do not have links for you at this time.