"Revocation information"

I installed NIS yesterday and today I am getting "Security Alert" pop up boxes when I try to access Internet sites, including Norton Support.  The box contains the following text:

 

"Revocation information for the security certificate for this site is not available.  Do your want to proceed?"

 

If I click "Yes" the box usually goes away and immediately returns.  After several clicks on "Yes" it finally goes away and the site can be accessed.  How can I get rid of this?

 

Thanks for any help.