Firefox Cert issues

I was online this morning and thought I was seeing an issue with my web connection.  After some successful ping tests and also seeing IE working properly, I noticed a SSL dialog was displaying behind my Firefox window (version 7.0.1) and thus prevented any other pages to load.

I closed and restarted my browser to get back to proper browsing.  I was also on Facebook, so it was very likely due to a certificate issue there.

Plugin wise, I run NoScript and Adblock Plus.  Just wanted to share for anyone who may encounter a similar issue.