Security Certificate Error NIS 2010

I keep getting this error " Revocation information for the security certificate for this site is not available.  Do you want to proceed?" when ever I try to use the chat support.  Even when I say to proceed I never get the chat site it just goes back to the first page.  I also see this error on my desktop everyday when I get home.  Why is this occurring and how do I fix it?

 

Windows XP Pro SP3.